diff --git a/Applications/Testing/Cpp/CMakeLists.txt b/Applications/Testing/Cpp/CMakeLists.txt
index 3a9ba51dab..b10938332d 100644
--- a/Applications/Testing/Cpp/CMakeLists.txt
+++ b/Applications/Testing/Cpp/CMakeLists.txt
@@ -33,7 +33,7 @@ if(CTK_APP_ctkDICOMQuery AND CTK_APP_ctkDICOMRetrieve)
   if(CTK_QT_VERSION VERSION_LESS "5")
     target_link_libraries(ctkDICOMApplicationTest1 ${QT_LIBRARIES})
   else()
-    target_link_libraries(ctkDICOMApplicationTest1 Qt5::Core)
+    target_link_libraries(ctkDICOMApplicationTest1 Qt${CTK_QT_VERSION}::Core)
   endif()
 
   ADD_TEST( NAME ctkDICOMApplicationTest1
diff --git a/Applications/ctkExampleHost/CMakeLists.txt b/Applications/ctkExampleHost/CMakeLists.txt
index 335ae2bb90..181ff06a3d 100644
--- a/Applications/ctkExampleHost/CMakeLists.txt
+++ b/Applications/ctkExampleHost/CMakeLists.txt
@@ -30,7 +30,7 @@ set(KIT_resources
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND KIT_target_libraries Qt5::Widgets)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Widgets)
 endif()
 
 ctkMacroBuildApp(
diff --git a/Applications/ctkPluginBrowser/CMakeLists.txt b/Applications/ctkPluginBrowser/CMakeLists.txt
index ecbc67d2d4..3ae5b4ef65 100644
--- a/Applications/ctkPluginBrowser/CMakeLists.txt
+++ b/Applications/ctkPluginBrowser/CMakeLists.txt
@@ -35,7 +35,7 @@ set(KIT_resources
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND KIT_target_libraries Qt5::Widgets)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Widgets)
 endif()
 
 ctkMacroBuildApp(
diff --git a/CMake/CMakeFindDependencyMacro.cmake b/CMake/CMakeFindDependencyMacro.cmake
index 2da2cf0231..225a3202f7 100644
--- a/CMake/CMakeFindDependencyMacro.cmake
+++ b/CMake/CMakeFindDependencyMacro.cmake
@@ -65,14 +65,16 @@ macro(find_dependency dep)
       set(cmake_fd_version ${ARGV1})
     endif()
     set(cmake_fd_exact_arg)
-    if(${ARGC} GREATER 2)
-      if (NOT "${ARGV2}" STREQUAL EXACT)
+    if(CTK_QT_VERSION VERSION_LESS "6")
+      if(${ARGC} GREATER 2)
+        if (NOT "${ARGV2}" STREQUAL EXACT)
+          message(FATAL_ERROR "Invalid arguments to find_dependency")
+        endif()
+        set(cmake_fd_exact_arg EXACT)
+      endif()
+      if(${ARGC} GREATER 3)
         message(FATAL_ERROR "Invalid arguments to find_dependency")
       endif()
-      set(cmake_fd_exact_arg EXACT)
-    endif()
-    if(${ARGC} GREATER 3)
-      message(FATAL_ERROR "Invalid arguments to find_dependency")
     endif()
     set(cmake_fd_quiet_arg)
     if(${CMAKE_FIND_PACKAGE_NAME}_FIND_QUIETLY)
diff --git a/CMake/ctkMacroBuildLib.cmake b/CMake/ctkMacroBuildLib.cmake
index 89f10e11b6..c2f0f58691 100644
--- a/CMake/ctkMacroBuildLib.cmake
+++ b/CMake/ctkMacroBuildLib.cmake
@@ -119,7 +119,7 @@ ${${MY_EXPORT_CUSTOM_CONTENT_FROM_VARIABLE}}
     # moc files can get very long and can't be resolved by the MSVC compiler.
     if(CTK_QT_VERSION VERSION_GREATER "4")
       foreach(moc_src ${MY_MOC_SRCS})
-        qt5_wrap_cpp(MY_MOC_CPP ${moc_src} OPTIONS -f${moc_src} OPTIONS -DHAVE_QT5)
+        qt_wrap_cpp(MY_MOC_CPP ${moc_src} OPTIONS -f${moc_src} OPTIONS "-DHAVE_QT${CTK_QT_VERSION}")
       endforeach()
     else()
       foreach(moc_src ${MY_MOC_SRCS})
@@ -130,8 +130,15 @@ ${${MY_EXPORT_CUSTOM_CONTENT_FROM_VARIABLE}}
   if(MY_GENERATE_MOC_SRCS)
     QT4_GENERATE_MOCS(${MY_GENERATE_MOC_SRCS})
   endif()
-  if(CTK_QT_VERSION VERSION_GREATER "4")
-    if(Qt5Widgets_FOUND)
+  if(CTK_QT_VERSION VERSION_GREATER "5")
+    if(Qt6Widgets_FOUND OR Qt6_FOUND)
+      qt_wrap_ui(MY_UI_CPP ${MY_UI_FORMS})
+    elseif(MY_UI_FORMS)
+      message(FATAL_ERROR "Argument UI_FORMS ignored because Qt6Widgets module was not specified")
+    endif()
+  elseif(CTK_QT_VERSION VERSION_GREATER "4")
+  MESSAGE(STATUS "CALLING QT WRAPUI 5")  
+  if(Qt5Widgets_FOUND)
       qt5_wrap_ui(MY_UI_CPP ${MY_UI_FORMS})
     elseif(MY_UI_FORMS)
       message(WARNING "Argument UI_FORMS ignored because Qt5Widgets module was not specified")
@@ -140,7 +147,9 @@ ${${MY_EXPORT_CUSTOM_CONTENT_FROM_VARIABLE}}
     QT4_WRAP_UI(MY_UI_CPP ${MY_UI_FORMS})
   endif()
   if(DEFINED MY_RESOURCES AND NOT MY_RESOURCES STREQUAL "")
-    if(CTK_QT_VERSION VERSION_GREATER "4")
+    if(CTK_QT_VERSION VERSION_GREATER "5")
+      qt_add_resources(MY_QRC_SRCS ${MY_RESOURCES})
+    elseif(CTK_QT_VERSION VERSION_GREATER "4")
       qt5_add_resources(MY_QRC_SRCS ${MY_RESOURCES})
     else()
       QT4_ADD_RESOURCES(MY_QRC_SRCS ${MY_RESOURCES})
diff --git a/CMake/ctkMacroBuildPlugin.cmake b/CMake/ctkMacroBuildPlugin.cmake
index e41ad9b599..c83f0959de 100644
--- a/CMake/ctkMacroBuildPlugin.cmake
+++ b/CMake/ctkMacroBuildPlugin.cmake
@@ -150,7 +150,7 @@ macro(ctkMacroBuildPlugin)
     # Add Qt include dirs and defines
     include(${QT_USE_FILE})
   else()
-    find_package(Qt5 COMPONENTS LinguistTools REQUIRED)
+    find_package(Qt${CTK_QT_VERSION} COMPONENTS LinguistTools REQUIRED)
   endif()
 
   # Add the library directories from the external project
@@ -316,16 +316,16 @@ macro(ctkMacroBuildPlugin)
       endforeach()
     endif()
   else()
-    find_package(Qt5LinguistTools REQUIRED)
+    find_package(Qt${CTK_QT_VERSION}LinguistTools REQUIRED)
   endif()
 
   if(MY_TEST_PLUGIN AND CTK_QT_VERSION VERSION_GREATER "4")
-    find_package(Qt5Test REQUIRED)
-    if(CMAKE_VERSION VERSION_LESS 2.8.12)
-      target_link_libraries(${lib_name} Qt5::Test)
-    else()
-      target_link_libraries(${lib_name} PRIVATE Qt5::Test)
-    endif()
+      find_package(Qt${CTK_QT_VERSION} Test REQUIRED)
+      if(CMAKE_VERSION VERSION_LESS 2.8.12)
+        target_link_libraries(${lib_name} Qt${CTK_QT_VERSION}::Test)
+      else()
+        target_link_libraries(${lib_name} PRIVATE Qt${CTK_QT_VERSION}::Test)
+      endif()
   endif()
 
   # Set the output directory for the plugin
diff --git a/CMake/ctkMacroBuildQtPlugin.cmake b/CMake/ctkMacroBuildQtPlugin.cmake
index 00af36bd80..b03e95da1f 100644
--- a/CMake/ctkMacroBuildQtPlugin.cmake
+++ b/CMake/ctkMacroBuildQtPlugin.cmake
@@ -89,13 +89,20 @@ macro(ctkMacroBuildQtPlugin)
   set(MY_QRC_SRCS "")
   if(CTK_QT_VERSION VERSION_GREATER "4")
     set(target)
-    if(Qt5Core_VERSION VERSION_GREATER "5.2.0")
+    if(Qt${CTK_QT_VERSION}Core_VERSION VERSION_GREATER "5.2.0")
       set(target TARGET ${MY_LIBNAME})
     endif()
-    qt5_wrap_cpp(MY_MOC_CPP ${MY_MOC_SRCS} OPTIONS -DHAVE_QT5 ${target})
-
+    if(CTK_QT_VERSION VERSION_GREATER "5")
+      qt_wrap_cpp(MY_MOC_CPP ${MY_MOC_SRCS} OPTIONS -DHAVE_QT${CTK_QT_VERSION} ${target})
+    else()
+      qt5_wrap_cpp(MY_MOC_CPP ${MY_MOC_SRCS} OPTIONS -DHAVE_QT${CTK_QT_VERSION} ${target})
+    endif()
     if(DEFINED MY_RESOURCES)
-      qt5_add_resources(MY_QRC_SRCS ${MY_RESOURCES})
+      if(CTK_QT_VERSION VERSION_GREATER "5")
+        qt_add_resources(MY_QRC_SRCS ${MY_RESOURCES})
+      else()
+        qt5_add_resources(MY_QRC_SRCS ${MY_RESOURCES})
+      endif()
     endif()
   else()
     QT4_WRAP_CPP(MY_MOC_CPP ${MY_MOC_SRCS})
@@ -191,9 +198,9 @@ endmacro()
 
 macro(ctkMacroBuildQtDesignerPlugin)
   if(CTK_QT_VERSION VERSION_GREATER "4")
-    find_package(Qt5 COMPONENTS Designer REQUIRED)
-    add_definitions(${Qt5Designer_DEFINITIONS})
-    include_directories(${Qt5Designer_INCLUDE_DIRS})
+    find_package(Qt${CTK_QT_VERSION} COMPONENTS Designer REQUIRED)
+    add_definitions(${Qt${CTK_QT_VERSION}Designer_DEFINITIONS})
+    include_directories(${Qt${CTK_QT_VERSION}Designer_INCLUDE_DIRS})
   endif()
   ctkMacroBuildQtPlugin(
     PLUGIN_DIR designer
@@ -205,7 +212,7 @@ macro(ctkMacroBuildQtDesignerPlugin)
       "SRCS;MOC_SRCS;UI_FORMS;INCLUDE_DIRECTORIES;TARGET_LIBRARIES;RESOURCES" # multi value args
       ${ARGN}
       )
-    target_link_libraries(${MY_NAME} Qt5::Designer)
+      target_link_libraries(${MY_NAME} Qt${CTK_QT_VERSION}::Designer)
   endif()
 endmacro()
 
diff --git a/CMake/ctkMacroGenerateMocs.cmake b/CMake/ctkMacroGenerateMocs.cmake
index 6306d995a4..a703a5a36a 100644
--- a/CMake/ctkMacroGenerateMocs.cmake
+++ b/CMake/ctkMacroGenerateMocs.cmake
@@ -5,7 +5,7 @@ include(MacroAddFileDependencies)
 
 function(_ctk_generate_mocs)
   if(CTK_QT_VERSION VERSION_GREATER "4")
-    if(Qt5_VERSION VERSION_LESS "5.15.0")
+    if(CTK_QT_VERSION VERSION_LESS "6")
       QT5_GET_MOC_FLAGS(_moc_flags)
     else()
        # _moc_flags is not needed because it is internally handled
@@ -29,17 +29,19 @@ function(_ctk_generate_mocs)
     endif()
 
     set(moc_file ${CMAKE_CURRENT_BINARY_DIR}/moc_${source_name}${source_ext})
-
-    if(CTK_QT_VERSION VERSION_GREATER "4")
+ 
+    if(CTK_QT_VERSION VERSION_GREATER "5")
+        qt_generate_moc(${abs_file} ${moc_file})
+    elseif(CTK_QT_VERSION VERSION_GREATER "4")
       if(Qt5_VERSION VERSION_LESS "5.6")
         QT5_CREATE_MOC_COMMAND(${abs_file} ${moc_file} "${_moc_flags}" "" "")
       elseif(Qt5_VERSION VERSION_LESS "5.15.0")
         QT5_CREATE_MOC_COMMAND(${abs_file} ${moc_file} "${_moc_flags}" "" "" "")
-      else()
+      elseif(Qt5_VERSION VERSION_LESS "6")
         # qt5_generate_moc internally calls qt5_get_moc_flags and ensure
         # no warnings are reported.
         qt5_generate_moc(${abs_file} ${moc_file})
-      endif()
+     endif()
     else()
       QT4_CREATE_MOC_COMMAND(${abs_file} ${moc_file} "${_moc_flags}" "" "")
     endif()
@@ -56,3 +58,9 @@ endmacro()
 macro(QT5_GENERATE_MOCS)
   _ctk_generate_mocs(${ARGN})
 endmacro()
+
+
+# create a Qt5 alias
+macro(QT6_GENERATE_MOCS)
+  _ctk_generate_mocs(${ARGN})
+endmacro()
diff --git a/CMake/ctkMacroSetupPlugins.cmake b/CMake/ctkMacroSetupPlugins.cmake
index 8f7428b73a..422ddeebb5 100644
--- a/CMake/ctkMacroSetupPlugins.cmake
+++ b/CMake/ctkMacroSetupPlugins.cmake
@@ -115,10 +115,10 @@ macro(ctkMacroSetupPlugins )
   # Qt shared libraries
   if (CTK_QT_VERSION VERSION_GREATER "4")
     if(WIN32)
-      get_target_property(_qt5_moc_executable Qt5::moc LOCATION)
+      get_target_property(_qt5_moc_executable Qt${CTK_QT_VERSION}::moc LOCATION)
       get_filename_component(QT_INSTALLED_LIBRARY_DIR ${_qt5_moc_executable} PATH)
     else()
-      get_target_property(_qt5_core_lib Qt5::Core LOCATION)
+      get_target_property(_qt5_core_lib Qt${CTK_QT_VERSION}::Core LOCATION)
       get_filename_component(QT_INSTALLED_LIBRARY_DIR ${_qt5_core_lib} PATH)
     endif()
   else()
diff --git a/CMake/ctkMacroSetupQt.cmake b/CMake/ctkMacroSetupQt.cmake
index 617420d372..3b0fa29023 100644
--- a/CMake/ctkMacroSetupQt.cmake
+++ b/CMake/ctkMacroSetupQt.cmake
@@ -23,22 +23,48 @@ macro(ctkMacroSetupQt)
   set(CTK_QT_VERSION "4" CACHE STRING "Expected Qt version")
   mark_as_advanced(CTK_QT_VERSION)
 
-  set_property(CACHE CTK_QT_VERSION PROPERTY STRINGS 4 5)
+  set_property(CACHE CTK_QT_VERSION PROPERTY STRINGS 4 5 6)
 
-  if(NOT (CTK_QT_VERSION VERSION_EQUAL "4" OR CTK_QT_VERSION VERSION_EQUAL "5"))
-    message(FATAL_ERROR "Expected value for CTK_QT_VERSION is either '4' or '5'")
+  if(NOT (CTK_QT_VERSION VERSION_EQUAL "4" OR CTK_QT_VERSION VERSION_EQUAL "5" OR CTK_QT_VERSION VERSION_EQUAL "6"))
+    message(FATAL_ERROR "Expected value for CTK_QT_VERSION is either '4' or '5' or '6'")
   endif()
 
+  if(CTK_QT_VERSION VERSION_GREATER "5")
+    cmake_minimum_required(VERSION 2.8.12)
+    find_package(Qt6 COMPONENTS Core)
+    set(CTK_QT6_COMPONENTS Core Xml Concurrent Sql Test StateMachine Core5Compat)
+    # XmlPatterns
+    if(CTK_ENABLE_Widgets OR CTK_LIB_Widgets OR CTK_LIB_CommandLineModules/Frontend/QtGui OR CTK_BUILD_ALL OR CTK_BUILD_ALL_LIBRARIES)
+      list(APPEND CTK_QT6_COMPONENTS Widgets OpenGL UiTools)
+    endif()
+    if(CTK_LIB_CommandLineModules/Frontend/QtWebKit OR CTK_BUILD_ALL OR CTK_BUILD_ALL_LIBRARIES)
+      if(TARGET Qt6::WebKitWidgets)
+        list(APPEND CTK_QT6_COMPONENTS WebKitWidgets)
+      else()
+        list(APPEND CTK_QT6_COMPONENTS WebEngineWidgets)
+      endif()
+    endif()
+    if(CTK_LIB_XNAT/Core OR CTK_BUILD_ALL OR CTK_BUILD_ALL_LIBRARIES)
+      list(APPEND CTK_QT6_COMPONENTS Script)
+    endif()
+    find_package(Qt6 COMPONENTS ${CTK_QT6_COMPONENTS} REQUIRED)
+
+    mark_as_superbuild(Qt6_DIR) # Qt 6
+
+    # XXX Backward compatible way
+    if(DEFINED CMAKE_PREFIX_PATH)
+      mark_as_superbuild(CMAKE_PREFIX_PATH) # Qt 6
+    endif()
 
-  if(CTK_QT_VERSION VERSION_GREATER "4")
+  elseif(CTK_QT_VERSION VERSION_GREATER "4")
     cmake_minimum_required(VERSION 2.8.12)
-    find_package(Qt5 COMPONENTS Core)
+    find_package(Qt${CTK_QT_VERSION} COMPONENTS Core)
     set(CTK_QT5_COMPONENTS Core Xml XmlPatterns Concurrent Sql Test Multimedia)
     if(CTK_ENABLE_Widgets OR CTK_LIB_Widgets OR CTK_LIB_CommandLineModules/Frontend/QtGui OR CTK_BUILD_ALL OR CTK_BUILD_ALL_LIBRARIES)
       list(APPEND CTK_QT5_COMPONENTS Widgets OpenGL UiTools)
     endif()
     if(CTK_LIB_CommandLineModules/Frontend/QtWebKit OR CTK_BUILD_ALL OR CTK_BUILD_ALL_LIBRARIES)
-      if(TARGET Qt5::WebKitWidgets)
+      if(TARGET Qt${CTK_QT_VERSION}::WebKitWidgets)
         list(APPEND CTK_QT5_COMPONENTS WebKitWidgets)
       else()
         list(APPEND CTK_QT5_COMPONENTS WebEngineWidgets)
@@ -47,7 +73,7 @@ macro(ctkMacroSetupQt)
     if(CTK_LIB_XNAT/Core OR CTK_BUILD_ALL OR CTK_BUILD_ALL_LIBRARIES)
       list(APPEND CTK_QT5_COMPONENTS Script)
     endif()
-    find_package(Qt5 COMPONENTS ${CTK_QT5_COMPONENTS} REQUIRED)
+    find_package(Qt${CTK_QT_VERSION} COMPONENTS ${CTK_QT5_COMPONENTS} REQUIRED)
 
     mark_as_superbuild(Qt5_DIR) # Qt 5
 
diff --git a/Libs/CommandLineModules/Core/CMakeLists.txt b/Libs/CommandLineModules/Core/CMakeLists.txt
index ce55df9e43..938b372dc6 100644
--- a/Libs/CommandLineModules/Core/CMakeLists.txt
+++ b/Libs/CommandLineModules/Core/CMakeLists.txt
@@ -79,8 +79,11 @@ set(KIT_resources
 # The following macro will read the target libraries from the file 'target_libraries.cmake'
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
+if(CTK_QT_VERSION VERSION_EQUAL "5")
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::XmlPatterns)
+endif()
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND KIT_target_libraries Qt5::XmlPatterns Qt5::Widgets Qt5::Concurrent)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Widgets Qt${CTK_QT_VERSION}::Concurrent)
 else()
   set(QT_USE_QTXMLPATTERNS 1)
   include(${QT_USE_FILE})
diff --git a/Libs/CommandLineModules/Core/Testing/Cpp/CMakeLists.txt b/Libs/CommandLineModules/Core/Testing/Cpp/CMakeLists.txt
index a913bba331..3b5e3ec816 100644
--- a/Libs/CommandLineModules/Core/Testing/Cpp/CMakeLists.txt
+++ b/Libs/CommandLineModules/Core/Testing/Cpp/CMakeLists.txt
@@ -50,7 +50,7 @@ ctk_add_executable_utf8(${KIT}CppTests ${Tests} ${Tests_SRCS} ${Tests_MOC_CPP} $
 target_link_libraries(${KIT}CppTests ${LIBRARY_NAME} ${CTK_BASE_LIBRARIES})
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  target_link_libraries(${KIT}CppTests Qt5::Test)
+  target_link_libraries(${KIT}CppTests Qt${CTK_QT_VERSION}::Test)
 endif()
 
 #
diff --git a/Libs/CommandLineModules/Frontend/QtGui/CMakeLists.txt b/Libs/CommandLineModules/Frontend/QtGui/CMakeLists.txt
index 3ad6dd1e6d..bc2d3e7934 100644
--- a/Libs/CommandLineModules/Frontend/QtGui/CMakeLists.txt
+++ b/Libs/CommandLineModules/Frontend/QtGui/CMakeLists.txt
@@ -41,9 +41,8 @@ set(KIT_resources
 # Target libraries - See CMake/ctkFunctionGetTargetLibraries.cmake
 # The following macro will read the target libraries from the file 'target_libraries.cmake'
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
-
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND KIT_target_libraries Qt5::UiTools Qt5::Widgets)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::UiTools Qt${CTK_QT_VERSION}::Widgets)
 else()
   set(QT_USE_QTUITOOLS 1)
   include(${QT_USE_FILE})
diff --git a/Libs/CommandLineModules/Frontend/QtGui/Testing/Cpp/CMakeLists.txt b/Libs/CommandLineModules/Frontend/QtGui/Testing/Cpp/CMakeLists.txt
index 4fa7d64a26..c927d269dd 100644
--- a/Libs/CommandLineModules/Frontend/QtGui/Testing/Cpp/CMakeLists.txt
+++ b/Libs/CommandLineModules/Frontend/QtGui/Testing/Cpp/CMakeLists.txt
@@ -53,7 +53,7 @@ ctk_add_executable_utf8(${KIT}CppTests ${Tests} ${Tests_SRCS} ${Tests_MOC_CPP} $
 target_link_libraries(${KIT}CppTests ${LIBRARY_NAME} ${CTK_BASE_LIBRARIES})
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  target_link_libraries(${KIT}CppTests Qt5::Test)
+  target_link_libraries(${KIT}CppTests Qt${CTK_QT_VERSION}::Test)
 endif()
 
 #
diff --git a/Libs/CommandLineModules/Frontend/QtWebKit/CMakeLists.txt b/Libs/CommandLineModules/Frontend/QtWebKit/CMakeLists.txt
index 234dd56d4d..dc744bacb4 100644
--- a/Libs/CommandLineModules/Frontend/QtWebKit/CMakeLists.txt
+++ b/Libs/CommandLineModules/Frontend/QtWebKit/CMakeLists.txt
@@ -37,10 +37,10 @@ set(KIT_resources
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  if(TARGET Qt5::WebKitWidgets)
-    list(APPEND KIT_target_libraries Qt5::WebKitWidgets)
+  if(TARGET Qt${CTK_QT_VERSION}::WebKitWidgets)
+    list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::WebKitWidgets)
   else()
-    list(APPEND KIT_target_libraries Qt5::WebEngineWidgets)
+    list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::WebEngineWidgets)
   endif()
 else()
   set(QT_USE_QTWEBKIT 1)
diff --git a/Libs/CommandLineModules/Testing/Cpp/CMakeLists.txt b/Libs/CommandLineModules/Testing/Cpp/CMakeLists.txt
index 58a290ae26..911055ec1c 100644
--- a/Libs/CommandLineModules/Testing/Cpp/CMakeLists.txt
+++ b/Libs/CommandLineModules/Testing/Cpp/CMakeLists.txt
@@ -97,7 +97,7 @@ target_link_libraries(${KIT}CppTests ${_additional_link_libraries})
 add_dependencies(${KIT}CppTests ctkCmdLineTestModules)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  target_link_libraries(${KIT}CppTests Qt5::Gui Qt5::Test)
+  target_link_libraries(${KIT}CppTests Qt${CTK_QT_VERSION}::Gui Qt${CTK_QT_VERSION}::Test)
 endif()
 
 if(TARGET CTKCommandLineModulesCoreCppTests)
diff --git a/Libs/CommandLineModules/Testing/Modules/CMakeLists.txt b/Libs/CommandLineModules/Testing/Modules/CMakeLists.txt
index 279ea1556d..77ed15c798 100644
--- a/Libs/CommandLineModules/Testing/Modules/CMakeLists.txt
+++ b/Libs/CommandLineModules/Testing/Modules/CMakeLists.txt
@@ -15,7 +15,7 @@ function(ctkFunctionCreateCmdLineModule name)
   if(CTK_QT_VERSION VERSION_LESS "5")
     target_link_libraries(ctkCmdLineModule${name} CTKCore ${QT_LIBRARIES})
   else()
-    target_link_libraries(ctkCmdLineModule${name} CTKCore Qt5::Widgets)
+    target_link_libraries(ctkCmdLineModule${name} CTKCore Qt${CTK_QT_VERSION}::Widgets)
   endif()
   add_dependencies(ctkCmdLineTestModules ctkCmdLineModule${name})
 endfunction()
diff --git a/Libs/Core/CMakeLists.txt b/Libs/Core/CMakeLists.txt
index 5c6c98b93c..2514d8f951 100644
--- a/Libs/Core/CMakeLists.txt
+++ b/Libs/Core/CMakeLists.txt
@@ -135,7 +135,9 @@ set(KIT_target_libraries)
 
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
-if(CTK_QT_VERSION VERSION_GREATER "4")
+if(CTK_QT_VERSION VERSION_GREATER "5")
+  list(APPEND KIT_target_libraries Qt6::Core Qt6::StateMachine Qt6::Core5Compat)
+elseif(CTK_QT_VERSION VERSION_GREATER "4")
   list(APPEND KIT_target_libraries Qt5::Core)
 endif()
 
@@ -169,6 +171,13 @@ if(CTK_WRAP_PYTHONQT_LIGHT)
     )
 endif()
 
+if( CTK_QT_VERSION VERSION_GREATER_EQUAL "6")
+set_property(
+    SOURCE moc_ctkWorkflow.cpp
+    PROPERTY COMPILE_DEFINITIONS
+      CTK_COMPILING_FROM_MOC_CPP
+  )
+endif()
 
 # Testing
 if(BUILD_TESTING)
diff --git a/Libs/Core/Documentation/Snippets/CommandLineParser/main.cpp b/Libs/Core/Documentation/Snippets/CommandLineParser/main.cpp
index 1d19fabe95..77d7012a79 100644
--- a/Libs/Core/Documentation/Snippets/CommandLineParser/main.cpp
+++ b/Libs/Core/Documentation/Snippets/CommandLineParser/main.cpp
@@ -2,6 +2,7 @@
 #include <ctkCommandLineParser.h>
 
 #include <QCoreApplication>
+#include <QIODevice>
 #include <QTextStream>
 
 #include <cstdlib>
diff --git a/Libs/Core/Testing/Cpp/CMakeLists.txt b/Libs/Core/Testing/Cpp/CMakeLists.txt
index d679dd3687..2ca344c9ed 100644
--- a/Libs/Core/Testing/Cpp/CMakeLists.txt
+++ b/Libs/Core/Testing/Cpp/CMakeLists.txt
@@ -105,8 +105,8 @@ set(Tests_Helpers_MOC_CPPS
 
 set(Tests_Helpers_MOC_CPP)
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  qt5_wrap_cpp(Tests_Helpers_MOC_CPP ${Tests_Helpers_MOC_SRCS})
-  qt5_generate_mocs(${Tests_Helpers_MOC_CPPS})
+  qt_wrap_cpp(Tests_Helpers_MOC_CPP ${Tests_Helpers_MOC_SRCS})
+  qt_generate_moc(${Tests_Helpers_MOC_CPPS})
 else()
   QT4_WRAP_CPP(Tests_Helpers_MOC_CPP ${Tests_Helpers_MOC_SRCS})
   QT4_GENERATE_MOCS(${Tests_Helpers_MOC_CPPS})
@@ -127,8 +127,8 @@ ctk_add_executable_utf8(${KIT}CppTests ${Tests} ${Tests_Helpers_SRCS} ${Tests_He
 target_link_libraries(${KIT}CppTests ${LIBRARY_NAME} ${CTK_BASE_LIBRARIES} CTKDummyPlugin)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  find_package(Qt5 COMPONENTS Test Widgets REQUIRED)
-  target_link_libraries(${KIT}CppTests Qt5::Test Qt5::Widgets)
+  find_package(Qt${CTK_QT_VERSION} COMPONENTS Test Widgets REQUIRED)
+  target_link_libraries(${KIT}CppTests Qt${CTK_QT_VERSION}::Test Qt${CTK_QT_VERSION}::Widgets)
 endif()
 
 if(UNIX AND NOT APPLE)
diff --git a/Libs/Core/Testing/Cpp/ctkBooleanMapperTest.cpp b/Libs/Core/Testing/Cpp/ctkBooleanMapperTest.cpp
index 097856c50e..9bf65ad205 100644
--- a/Libs/Core/Testing/Cpp/ctkBooleanMapperTest.cpp
+++ b/Libs/Core/Testing/Cpp/ctkBooleanMapperTest.cpp
@@ -176,4 +176,7 @@ void ctkBooleanMapperTester::testSignals()
 
 // ----------------------------------------------------------------------------
 CTK_TEST_MAIN(ctkBooleanMapperTest)
-#include "moc_ctkBooleanMapperTest.cpp"
+
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+  #include "moc_ctkBooleanMapperTest.cpp"
+#endif
\ No newline at end of file
diff --git a/Libs/Core/Testing/Cpp/ctkLinearValueProxyTest.cpp b/Libs/Core/Testing/Cpp/ctkLinearValueProxyTest.cpp
index c16630d4b8..e45ceb18e2 100644
--- a/Libs/Core/Testing/Cpp/ctkLinearValueProxyTest.cpp
+++ b/Libs/Core/Testing/Cpp/ctkLinearValueProxyTest.cpp
@@ -506,4 +506,6 @@ void ctkLinearValueProxyTester::testProxyModified_data()
 
 // ----------------------------------------------------------------------------
 CTK_TEST_MAIN(ctkLinearValueProxyTest)
-#include "moc_ctkLinearValueProxyTest.cpp"
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+  #include "moc_ctkLinearValueProxyTest.cpp"
+#endif
diff --git a/Libs/Core/Testing/Cpp/ctkUtilsTest.cpp b/Libs/Core/Testing/Cpp/ctkUtilsTest.cpp
index 8a5b57e292..7c5455756a 100644
--- a/Libs/Core/Testing/Cpp/ctkUtilsTest.cpp
+++ b/Libs/Core/Testing/Cpp/ctkUtilsTest.cpp
@@ -305,5 +305,7 @@ Q_DECLARE_METATYPE (QSet<QString>)
 
 // ----------------------------------------------------------------------------
 CTK_TEST_MAIN(ctkUtilsTest)
-#include "moc_ctkUtilsTest.cpp"
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+  #include "moc_ctkUtilsTest.cpp"
+#endif
 
diff --git a/Libs/Core/ctkCommandLineParser.cpp b/Libs/Core/ctkCommandLineParser.cpp
index 22bf017462..f9a1743c52 100644
--- a/Libs/Core/ctkCommandLineParser.cpp
+++ b/Libs/Core/ctkCommandLineParser.cpp
@@ -31,6 +31,7 @@
 
 // CTK includes
 #include "ctkCommandLineParser.h"
+#include <QRegExp>
 
 namespace
 {
diff --git a/Libs/Core/ctkErrorLogAbstractModel.cpp b/Libs/Core/ctkErrorLogAbstractModel.cpp
index 11e904b423..872c739758 100644
--- a/Libs/Core/ctkErrorLogAbstractModel.cpp
+++ b/Libs/Core/ctkErrorLogAbstractModel.cpp
@@ -376,10 +376,18 @@ void ctkErrorLogAbstractModel::filterEntry(const ctkErrorLogLevel::LogLevels& lo
   Q_D(ctkErrorLogAbstractModel);
 
   QStringList patterns;
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   if (!this->filterRegExp().pattern().isEmpty())
     {
     patterns << this->filterRegExp().pattern().split("|");
     }
+#else
+  if (!this->filterRegularExpression().pattern().isEmpty())
+    {
+    patterns << this->filterRegularExpression().pattern().split("|");
+    }
+
+#endif
   patterns.removeAll(d->ErrorLogLevel(ctkErrorLogLevel::None));
 
 //  foreach(QString s, patterns)
@@ -419,7 +427,11 @@ void ctkErrorLogAbstractModel::filterEntry(const ctkErrorLogLevel::LogLevels& lo
     }
 
   bool filterChanged = true;
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   QStringList currentPatterns = this->filterRegExp().pattern().split("|");
+#else
+  QStringList currentPatterns = this->filterRegularExpression().pattern().split("|");
+#endif
   if (currentPatterns.count() == patterns.count())
     {
     foreach(const QString& p, patterns)
@@ -428,9 +440,11 @@ void ctkErrorLogAbstractModel::filterEntry(const ctkErrorLogLevel::LogLevels& lo
       }
     filterChanged = currentPatterns.count() > 0;
     }
-
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   this->setFilterRegExp(patterns.join("|"));
-
+#else
+  this->setFilterRegularExpression(patterns.join("|"));
+#endif
   if (filterChanged)
     {
     emit this->logLevelFilterChanged();
@@ -445,10 +459,17 @@ ctkErrorLogLevel::LogLevels ctkErrorLogAbstractModel::logLevelFilter()const
   Q_ASSERT(QString("LogLevel").compare(logLevelEnum.name()) == 0);
 
   ctkErrorLogLevel::LogLevels filter = ctkErrorLogLevel::Unknown;
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   foreach(const QString& filterAsString, this->filterRegExp().pattern().split("|"))
     {
     filter |= static_cast<ctkErrorLogLevel::LogLevels>(logLevelEnum.keyToValue(filterAsString.toLatin1()));
     }
+#else
+  foreach(const QString& filterAsString, this->filterRegularExpression().pattern().split("|"))
+    {
+    filter |= static_cast<ctkErrorLogLevel::LogLevels>(logLevelEnum.keyToValue(filterAsString.toLatin1()));
+    }
+#endif
   return filter;
 }
 
diff --git a/Libs/Core/ctkUtils.cpp b/Libs/Core/ctkUtils.cpp
index 776893398b..3e3801ab30 100644
--- a/Libs/Core/ctkUtils.cpp
+++ b/Libs/Core/ctkUtils.cpp
@@ -21,7 +21,11 @@
 // Qt includes
 #include <QDebug>
 #include <QDir>
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+#include <QRegularExpression>
+#else
 #include <QRegExp>
+#endif
 #include <QString>
 #include <QStringList>
 
@@ -109,17 +113,30 @@ const char *ctkValidWildCard =
 QStringList ctk::nameFilterToExtensions(const QString& nameFilter)
 {
   QRegExp regexp(QString::fromLatin1(ctkNameFilterRegExp));
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+  int i = nameFilter.indexOf(regexp);
+#else
   int i = regexp.indexIn(nameFilter);
+#endif
   if (i < 0)
     {
     QRegExp isWildCard(QString::fromLatin1(ctkValidWildCard));
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+    if (nameFilter.indexOf(isWildCard) >= 0)
+#else
     if (isWildCard.indexIn(nameFilter) >= 0)
+#endif
       {
       return QStringList(nameFilter);
       }
     return QStringList();
     }
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+  QStringList captured = regexp.namedCaptureGroups();
+  QString f = captured.size() >= 3 ? captured[2] : "";
+#else
   QString f = regexp.cap(2);
+#endif
   #if (QT_VERSION >= QT_VERSION_CHECK(5, 14, 0))
   return f.split(QLatin1Char(' '), Qt::SkipEmptyParts);
   #else
@@ -143,12 +160,22 @@ QString ctk::extensionToRegExp(const QString& extension)
 {
   // typically *.jpg
   QRegExp extensionExtractor("\\*\\.(\\w+)");
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+  int pos = extension.indexOf(extensionExtractor);
+#else
   int pos = extensionExtractor.indexIn(extension);
+#endif
   if (pos < 0)
     {
     return QString();
     }
-  return ".*\\." + extensionExtractor.cap(1) + "?$";
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+  QStringList captured = extensionExtractor.namedCaptureGroups();
+  QString cap = captured.size() >= 2 ? captured[1] : "";
+#else
+  QString cap = extensionExtractor.cap(1);
+#endif
+  return ".*\\." + cap + "?$";
 }
 
 //-----------------------------------------------------------------------------
diff --git a/Libs/Core/ctkUtils.h b/Libs/Core/ctkUtils.h
index 5ddd7c774f..605f9e3e1d 100644
--- a/Libs/Core/ctkUtils.h
+++ b/Libs/Core/ctkUtils.h
@@ -28,6 +28,10 @@
 #include <QModelIndex>
 #include <QStringList>
 
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+#define QRegExp QRegularExpression
+#endif
+
 // STD includes
 #include <vector>
 
diff --git a/Libs/Core/ctkWorkflow.h b/Libs/Core/ctkWorkflow.h
index 43cbdf83b6..e208192dc3 100644
--- a/Libs/Core/ctkWorkflow.h
+++ b/Libs/Core/ctkWorkflow.h
@@ -251,5 +251,10 @@ protected Q_SLOTS:
   Q_DISABLE_COPY(ctkWorkflow);
 };
 
+#if defined(CTK_COMPILING_FROM_MOC_CPP)
+  #include "ctkWorkflowStep.h"
+#endif
+
+
 #endif
 
diff --git a/Libs/DICOM/Core/CMakeLists.txt b/Libs/DICOM/Core/CMakeLists.txt
index d2b7d8c60f..ee14b0109b 100644
--- a/Libs/DICOM/Core/CMakeLists.txt
+++ b/Libs/DICOM/Core/CMakeLists.txt
@@ -89,7 +89,7 @@ set(KIT_resources
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND KIT_target_libraries Qt5::Sql)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Sql)
 endif()
 
 # create a dcm query/retrieve service config file that points to the build dir
diff --git a/Libs/DICOM/Widgets/Testing/Cpp/CMakeLists.txt b/Libs/DICOM/Widgets/Testing/Cpp/CMakeLists.txt
index d198b7beb5..9ffe821e07 100644
--- a/Libs/DICOM/Widgets/Testing/Cpp/CMakeLists.txt
+++ b/Libs/DICOM/Widgets/Testing/Cpp/CMakeLists.txt
@@ -28,9 +28,13 @@ include_directories(
 
 set(CTK_QT_TEST_LIBRARY )
 
-if (CTK_QT_VERSION VERSION_GREATER "4")
-  find_package(Qt5Test REQUIRED)
-  set(CTK_QT_TEST_LIBRARY Qt5::Test)
+if (CTK_QT_VERSION VERSION_GREATER "5")
+  find_package(Qt6Test REQUIRED)
+  set(CTK_QT_TEST_LIBRARY Qt6::Test)
+  qt_generate_mocs(${Tests_MOC_CPPS})
+elseif (CTK_QT_VERSION VERSION_GREATER "4")
+  find_package(Qt${CTK_QT_VERSION}Test REQUIRED)
+  set(CTK_QT_TEST_LIBRARY Qt${CTK_QT_VERSION}::Test)
   qt5_generate_mocs(${Tests_MOC_CPPS})
 else()
   qt4_generate_mocs(${Tests_MOC_CPPS})
diff --git a/Libs/PluginFramework/CMakeLists.txt b/Libs/PluginFramework/CMakeLists.txt
index 06f8db9a4c..75f7c99353 100644
--- a/Libs/PluginFramework/CMakeLists.txt
+++ b/Libs/PluginFramework/CMakeLists.txt
@@ -158,7 +158,7 @@ set(KIT_resources
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND KIT_target_libraries Qt5::Sql Qt5::Concurrent)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Sql Qt${CTK_QT_VERSION}::Concurrent)
 endif()
 
 # Create a MANIFEST.MF resource for the PluginFramework library,
diff --git a/Libs/PluginFramework/Testing/Cpp/CMakeLists.txt b/Libs/PluginFramework/Testing/Cpp/CMakeLists.txt
index f3ca856c8c..69713f3b3f 100644
--- a/Libs/PluginFramework/Testing/Cpp/CMakeLists.txt
+++ b/Libs/PluginFramework/Testing/Cpp/CMakeLists.txt
@@ -21,5 +21,5 @@ add_library(${lib_name} SHARED ${SRCS} ${MY_MOC_CXX})
 target_link_libraries(${lib_name} ${fw_lib})
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  target_link_libraries(${lib_name} Qt5::Test)
+  target_link_libraries(${lib_name} Qt${CTK_QT_VERSION}::Test)
 endif()
diff --git a/Libs/PluginFramework/Testing/FrameworkTestPlugins/app_test/CMakeLists.txt b/Libs/PluginFramework/Testing/FrameworkTestPlugins/app_test/CMakeLists.txt
index 1571256fcb..422e399bd6 100644
--- a/Libs/PluginFramework/Testing/FrameworkTestPlugins/app_test/CMakeLists.txt
+++ b/Libs/PluginFramework/Testing/FrameworkTestPlugins/app_test/CMakeLists.txt
@@ -51,7 +51,7 @@ target_link_libraries(${test_executable}
 )
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  target_link_libraries(${test_executable} Qt5::Test)
+  target_link_libraries(${test_executable} Qt{CTK_QT_VERSION}::Test)
 endif()
 
 add_dependencies(${test_executable} ${PROJECT_NAME})
diff --git a/Libs/PluginFramework/Testing/FrameworkTestPlugins/pluginD_test/CMakeLists.txt b/Libs/PluginFramework/Testing/FrameworkTestPlugins/pluginD_test/CMakeLists.txt
index 7a519b8dd6..81b94dac75 100644
--- a/Libs/PluginFramework/Testing/FrameworkTestPlugins/pluginD_test/CMakeLists.txt
+++ b/Libs/PluginFramework/Testing/FrameworkTestPlugins/pluginD_test/CMakeLists.txt
@@ -17,7 +17,7 @@ add_library(${lib_name} SHARED ${PLUGIN_SRCS})
 if(CTK_QT_VERSION VERSION_LESS "5")
   target_link_libraries(${lib_name} ${QT_LIBRARIES})
 else()
-  target_link_libraries(${lib_name} Qt5::Core)
+  target_link_libraries(${lib_name} Qt${CTK_QT_VERSION}::Core)
 endif()
 
 # Apply properties to the library target.
diff --git a/Libs/QtTesting/CMakeLists.txt b/Libs/QtTesting/CMakeLists.txt
index 846207740d..eaa553bfc5 100644
--- a/Libs/QtTesting/CMakeLists.txt
+++ b/Libs/QtTesting/CMakeLists.txt
@@ -151,7 +151,7 @@ set(QtTesting_LIBRARIES QtTesting)
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND KIT_target_libraries Qt5::Xml Qt5::XmlPatterns)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Xml Qt${CTK_QT_VERSION}::XmlPatterns)
 endif()
 
 ctkMacroBuildLib(
diff --git a/Libs/Scripting/Python/Core/Testing/Cpp/CMakeLists.txt b/Libs/Scripting/Python/Core/Testing/Cpp/CMakeLists.txt
index 31593d59d3..eb395a13e8 100644
--- a/Libs/Scripting/Python/Core/Testing/Cpp/CMakeLists.txt
+++ b/Libs/Scripting/Python/Core/Testing/Cpp/CMakeLists.txt
@@ -14,10 +14,15 @@ include_directories(${CMAKE_SOURCE_DIR}/Libs/Testing
                     ${CMAKE_CURRENT_BINARY_DIR})
 
 set(CTK_QT_TEST_LIBRARY )
-
-if (CTK_QT_VERSION VERSION_GREATER "4")
-  find_package(Qt5Test REQUIRED)
-  set(CTK_QT_TEST_LIBRARY Qt5::Test)
+if (CTK_QT_VERSION VERSION_GREATER "5")
+  find_package(Qt6Test REQUIRED)
+  set(CTK_QT_TEST_LIBRARY Qt6::Test)
+  QT6_GENERATE_MOCS(
+    ctkAbstractPythonManagerTest.cpp
+    )
+elseif (CTK_QT_VERSION VERSION_GREATER "4")
+  find_package(Qt${CTK_QT_VERSION}Test REQUIRED)
+  set(CTK_QT_TEST_LIBRARY Qt${CTK_QT_VERSION}::Test)
   QT5_GENERATE_MOCS(
     ctkAbstractPythonManagerTest.cpp
     )
diff --git a/Libs/Widgets/CMakeLists.txt b/Libs/Widgets/CMakeLists.txt
index c272782ffb..ddb3981fcd 100644
--- a/Libs/Widgets/CMakeLists.txt
+++ b/Libs/Widgets/CMakeLists.txt
@@ -353,7 +353,9 @@ set(KIT_resources
 # The following macro will read the target libraries from the file 'target_libraries.cmake'
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
-if(CTK_QT_VERSION VERSION_GREATER "4")
+if(CTK_QT_VERSION VERSION_GREATER "5")
+  list(APPEND KIT_target_libraries Qt6::Widgets Qt6::Xml Qt6::OpenGL Qt6::OpenGLWidgets)
+elseif(CTK_QT_VERSION VERSION_GREATER "4")
   list(APPEND KIT_target_libraries Qt5::Widgets Qt5::Xml Qt5::OpenGL)
 endif()
 
@@ -474,3 +476,11 @@ endif()
 if(BUILD_TESTING)
   add_subdirectory(Testing)
 endif()
+
+if( CTK_QT_VERSION VERSION_GREATER_EQUAL "6")
+set_property(
+    SOURCE moc_ctkSettingsDialog.cpp
+    PROPERTY COMPILE_DEFINITIONS
+      CTK_COMPILING_FROM_MOC_CPP
+  )
+endif()
diff --git a/Libs/Widgets/Plugins/ctkPopupWidgetPlugin.cpp b/Libs/Widgets/Plugins/ctkPopupWidgetPlugin.cpp
index ea39f9cfe6..a1e607c954 100644
--- a/Libs/Widgets/Plugins/ctkPopupWidgetPlugin.cpp
+++ b/Libs/Widgets/Plugins/ctkPopupWidgetPlugin.cpp
@@ -33,7 +33,7 @@ QWidget *ctkPopupWidgetPlugin::createWidget(QWidget* widgetParent)
 {
   ctkPopupWidget* newWidget = new ctkPopupWidget(widgetParent);
   // if the widget is a tooltip, it wouldn't accept children
-  newWidget->setWindowFlags(0);
+  newWidget->setWindowFlags(Qt::Widget);
   // if the widget auto hides, it disappear from the workplace and don't allow
   // children anymore.
   newWidget->setAutoHide(false);
diff --git a/Libs/Widgets/Plugins/ctkWidgetsPlugins.h b/Libs/Widgets/Plugins/ctkWidgetsPlugins.h
index de893fdce6..124cea0971 100644
--- a/Libs/Widgets/Plugins/ctkWidgetsPlugins.h
+++ b/Libs/Widgets/Plugins/ctkWidgetsPlugins.h
@@ -80,10 +80,10 @@ class CTK_WIDGETS_PLUGINS_EXPORT ctkWidgetsPlugins
   , public QDesignerCustomWidgetCollectionInterface
 {
   Q_OBJECT
-  Q_INTERFACES(QDesignerCustomWidgetCollectionInterface)
 #ifdef HAVE_QT5
   Q_PLUGIN_METADATA(IID "org.commontk.Widgets")
 #endif
+  Q_INTERFACES(QDesignerCustomWidgetCollectionInterface)
 public:
   QList<QDesignerCustomWidgetInterface*> customWidgets() const
     {
diff --git a/Libs/Widgets/Testing/Cpp/CMakeLists.txt b/Libs/Widgets/Testing/Cpp/CMakeLists.txt
index a0bc6d6bdf..2a9f5449e3 100644
--- a/Libs/Widgets/Testing/Cpp/CMakeLists.txt
+++ b/Libs/Widgets/Testing/Cpp/CMakeLists.txt
@@ -250,11 +250,13 @@ endif()
 
 ctk_add_executable_utf8(${KIT}CppTests ${Tests} ${Tests_SRCS} ${Tests_MOC_CPP} ${Tests_UI_CPP} ${Tests_RESOURCES_SRCS})
 target_link_libraries(${KIT}CppTests ${LIBRARY_NAME})
-
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND KIT_target_libraries Qt5::Test)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Test)
   if(CTK_USE_QTTESTING)
-    list(APPEND KIT_target_libraries Qt5::Xml Qt5::XmlPatterns)
+    list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Xml)
+    if(CTK_QT_VERSION VERSION_EQUAL 5)
+      list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::XmlPatterns)
+    endif()
   endif()
   target_link_libraries(${KIT}CppTests ${KIT_target_libraries})
 endif()
diff --git a/Libs/Widgets/ctkActionsWidget.cpp b/Libs/Widgets/ctkActionsWidget.cpp
index f9e5a29274..ef714babfb 100644
--- a/Libs/Widgets/ctkActionsWidget.cpp
+++ b/Libs/Widgets/ctkActionsWidget.cpp
@@ -22,6 +22,7 @@
 #include <QAction>
 #include <QDebug>
 #include <QHeaderView>
+#include <QMenu>
 #include <QPainter>
 #include <QSortFilterProxyModel>
 #include <QStandardItem>
@@ -30,6 +31,7 @@
 #include <QTreeView>
 #include <QVBoxLayout>
 
+
 // CTK includes
 #include "ctkActionsWidget.h"
 
diff --git a/Libs/Widgets/ctkBasePopupWidget.cpp b/Libs/Widgets/ctkBasePopupWidget.cpp
index 8348161c7e..0962eea117 100644
--- a/Libs/Widgets/ctkBasePopupWidget.cpp
+++ b/Libs/Widgets/ctkBasePopupWidget.cpp
@@ -21,7 +21,9 @@
 // Qt includes
 #include <QApplication>
 #include <QDebug>
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
 #include <QDesktopWidget>
+#endif
 #include <QDir>
 #include <QEvent>
 #include <QLabel>
diff --git a/Libs/Widgets/ctkCheckableComboBox.cpp b/Libs/Widgets/ctkCheckableComboBox.cpp
index 75ee9ca126..6d85c0a2de 100644
--- a/Libs/Widgets/ctkCheckableComboBox.cpp
+++ b/Libs/Widgets/ctkCheckableComboBox.cpp
@@ -22,7 +22,6 @@
 #include <QApplication>
 #include <QAbstractItemView>
 #include <QDebug>
-#include <QDesktopWidget>
 #include <QItemDelegate>
 #include <QLayout>
 #include <QMouseEvent>
diff --git a/Libs/Widgets/ctkCheckablePushButton.cpp b/Libs/Widgets/ctkCheckablePushButton.cpp
index 50f29d02da..9c575f5e42 100644
--- a/Libs/Widgets/ctkCheckablePushButton.cpp
+++ b/Libs/Widgets/ctkCheckablePushButton.cpp
@@ -21,7 +21,6 @@
 // Qt includes
 #include <QApplication>
 #include <QDebug>
-#include <QDesktopWidget>
 #include <QLayout>
 #include <QMouseEvent>
 #include <QMenu>
@@ -87,8 +86,11 @@ QStyleOptionButton ctkCheckablePushButtonPrivate::drawIcon(QPainter* p)
   Q_Q(ctkCheckablePushButton);
 
   QStyleOptionButton indicatorOpt;
-
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+  indicatorOpt.initFrom(q);
+#else
   indicatorOpt.init(q);
+#endif
   if (!this->CheckBoxUserCheckable)
     {
     indicatorOpt.state &= ~QStyle::State_Enabled;
diff --git a/Libs/Widgets/ctkCollapsibleButton.cpp b/Libs/Widgets/ctkCollapsibleButton.cpp
index d9218e3468..7439f2c7d2 100644
--- a/Libs/Widgets/ctkCollapsibleButton.cpp
+++ b/Libs/Widgets/ctkCollapsibleButton.cpp
@@ -30,7 +30,9 @@
 #include <QPushButton>
 #include <QStyle>
 #include <QStyleOptionButton>
+#if QT_VERSION < QT_VERSION_CHECK(5,0,0)
 #include <QStyleOptionFrameV3>
+#endif
 
 // CTK includes
 #include "ctkCollapsibleButton.h"
@@ -450,8 +452,13 @@ QSize ctkCollapsibleButton::buttonSizeHint()const
     }
   h = qMax(h, sz.height());
   //opt.rect.setSize(QSize(w, h)); // PM_MenuButtonIndicator depends on the height
+  #if (QT_VERSION < QT_VERSION_CHECK(6,0,0))
   QSize buttonSize = (style()->sizeFromContents(QStyle::CT_PushButton, &opt, QSize(w, h), this).
                       expandedTo(QApplication::globalStrut()));
+  #else
+  QSize buttonSize = style()->sizeFromContents(QStyle::CT_PushButton, &opt, QSize(w, h), this);
+  #endif
+
   return buttonSize;
 }
 
@@ -558,7 +565,11 @@ void ctkCollapsibleButton::paintEvent(QPaintEvent * _event)
   int buttonMargin = this->style()->pixelMetric(QStyle::PM_ButtonMargin, &opt, this);
   // Draw Indicator
   QStyleOption indicatorOpt;
+#if (QT_VERSION < QT_VERSION_CHECK(6,0,0))
   indicatorOpt.init(this);
+#else
+  indicatorOpt.initFrom(this);
+#endif
   if (d->IndicatorAlignment & Qt::AlignLeft)
     {
     indicatorOpt.rect = QRect((buttonHeight - indicatorSize.width()) / 2,
@@ -652,7 +663,11 @@ void ctkCollapsibleButton::paintEvent(QPaintEvent * _event)
 #else
   QStyleOptionFrame fopt;
 #endif
-  fopt.init(this);
+  #if (QT_VERSION < QT_VERSION_CHECK(6,0,0))
+    fopt.init(this);
+  #else
+    fopt.initFrom(this);
+  #endif
   // HACK: on some styles, the frame doesn't exactly touch the button.
   // this is because the button has some kind of extra border.
 #if QT_VERSION < QT_VERSION_CHECK(5,0,0)
diff --git a/Libs/Widgets/ctkColorPickerButton.cpp b/Libs/Widgets/ctkColorPickerButton.cpp
index 98ace0aa87..32f00719f1 100644
--- a/Libs/Widgets/ctkColorPickerButton.cpp
+++ b/Libs/Widgets/ctkColorPickerButton.cpp
@@ -297,17 +297,24 @@ QSize ctkColorPickerButton::sizeHint()const
     opt.iconSize = QSize(iconSize, iconSize);
     opt.rect.setSize(opt.iconSize); // PM_MenuButtonIndicator depends on the height
     d->CachedSizeHint = this->style()->sizeFromContents(
-      QStyle::CT_ToolButton, &opt, opt.iconSize, this).
-      expandedTo(QApplication::globalStrut());
+      QStyle::CT_ToolButton, &opt, opt.iconSize, this)
+      #if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+        .expandedTo(QApplication::globalStrut())
+      #endif
+      ;
     }
   else
     {
     pushButtonOpt.icon = d->Icon;
     pushButtonOpt.iconSize = QSize(iconSize, iconSize);
     pushButtonOpt.rect.setSize(pushButtonOpt.iconSize); // PM_MenuButtonIndicator depends on the height
-    d->CachedSizeHint = (style()->sizeFromContents(
-                           QStyle::CT_PushButton, &pushButtonOpt, pushButtonOpt.iconSize, this).
-                         expandedTo(QApplication::globalStrut()));
+    d->CachedSizeHint = style()->sizeFromContents(
+                           QStyle::CT_PushButton, &pushButtonOpt, pushButtonOpt.iconSize, this)
+                           #if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+                            .expandedTo(QApplication::globalStrut())
+                           #endif
+                          ;
+
     }
   return d->CachedSizeHint;
 }
diff --git a/Libs/Widgets/ctkComboBox.cpp b/Libs/Widgets/ctkComboBox.cpp
index 21192f59c0..b53f06fb05 100644
--- a/Libs/Widgets/ctkComboBox.cpp
+++ b/Libs/Widgets/ctkComboBox.cpp
@@ -65,7 +65,11 @@ QSize ctkComboBoxPrivate::recomputeSizeHint(QSize &sh) const
   Q_Q(const ctkComboBox);
   if (sh.isValid())
     {
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+    return sh;
+#else      
     return sh.expandedTo(QApplication::globalStrut());
+#endif
     }
 
   bool hasIcon = false;
@@ -151,7 +155,11 @@ QSize ctkComboBoxPrivate::recomputeSizeHint(QSize &sh) const
   QStyleOptionComboBox opt;
   this->initStyleOption(&opt);
   sh = q->style()->sizeFromContents(QStyle::CT_ComboBox, &opt, sh, q);
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+  return sh;
+#else
   return sh.expandedTo(QApplication::globalStrut());
+#endif
 }
 
 // -------------------------------------------------------------------------
diff --git a/Libs/Widgets/ctkCompleter.cpp b/Libs/Widgets/ctkCompleter.cpp
index 86f8030474..89e2bc6a9c 100644
--- a/Libs/Widgets/ctkCompleter.cpp
+++ b/Libs/Widgets/ctkCompleter.cpp
@@ -22,7 +22,9 @@
 #include <QDebug>
 #include <QSortFilterProxyModel>
 #include <QStringList>
-
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+#define QRegExp QRegularExpression
+#endif
 // CTK includes
 #include "ctkCompleter.h"
 
@@ -87,9 +89,14 @@ QStringList ctkCompleterPrivate::splitPath(const QString& s)
     case ctkCompleter::FilterWordStartsWith:
       {
       this->updateSortFilterProxyModel();
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+      QRegularExpression regexp = QRegularExpression(QRegularExpression::escape(s), QRegularExpression::PatternOption::CaseInsensitiveOption);
+      this->SortFilterProxyModel->setFilterRegularExpression(regexp);
+#else
       QRegExp regexp = QRegExp(QRegExp::escape(s));
       regexp.setCaseSensitivity(q->caseSensitivity());
       this->SortFilterProxyModel->setFilterRegExp(regexp);
+#endif
       paths = QStringList();
       break;
       }
diff --git a/Libs/Widgets/ctkConsole.cpp b/Libs/Widgets/ctkConsole.cpp
index 589d93bb56..63c6ff3d56 100644
--- a/Libs/Widgets/ctkConsole.cpp
+++ b/Libs/Widgets/ctkConsole.cpp
@@ -71,6 +71,11 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "ctkConsole_p.h"
 #include "ctkPimpl.h"
 
+//QT6 compatibility
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+#include <QRegularExpression>
+#define QRegExp QRegularExpression
+#endif
 //-----------------------------------------------------------------------------
 // ctkConsoleCompleter methods
 
@@ -152,7 +157,9 @@ void ctkConsolePrivate::init()
   this->RunFileButton->setVisible(false);
 
   QVBoxLayout * layout = new QVBoxLayout(q);
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   layout->setMargin(0);
+#endif
   layout->setSpacing(0);
   layout->addWidget(this);
   layout->addWidget(this->RunFileButton);
@@ -323,30 +330,30 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
       }
     }
 
-  QTextCursor textCursor = this->textCursor();
+  QTextCursor text_cursor = this->textCursor();
 
   // Set to true if there's a current selection
-  const bool selection = (textCursor.anchor() != textCursor.position());
+  const bool selection = text_cursor.anchor() != text_cursor.position();
   // Set to true if the cursor overlaps the history area
-  bool history_area = this->isCursorInHistoryArea();
+  const bool history_area = this->isCursorInHistoryArea();
   // The message output area is defined just under the command line
   // and it can display all messages catch during we autocomplete, etc.
   // Set to true if the cursor overlaps the message output area
-  bool message_output_area = this->isCursorInMessageOutputArea();
+  const bool message_output_area = this->isCursorInMessageOutputArea();
 
   if (e->key() == Qt::Key_Escape)
     {
     if (selection)
       {
       // if a selection is active then Esc removes it
-      textCursor.setPosition(textCursor.position());
-      this->setTextCursor(textCursor);
+      text_cursor.setPosition(text_cursor.position());
+      this->setTextCursor(text_cursor);
       }
     else if (history_area || message_output_area)
       {
       // if not in the interactive area then Esc moves back to the end of the interactive area
-      textCursor.setPosition(this->commandEnd());
-      this->setTextCursor(textCursor);
+      text_cursor.setPosition(this->commandEnd());
+      this->setTextCursor(text_cursor);
       }
     else
       {
@@ -390,8 +397,8 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
     {
     if(history_area || message_output_area)
       {
-      textCursor.setPosition(this->commandEnd());
-      this->setTextCursor(textCursor);
+      text_cursor.setPosition(this->commandEnd());
+      this->setTextCursor(text_cursor);
       }
     this->paste();
     this->updateCommandBuffer();
@@ -427,10 +434,8 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
        && e->key() != Qt::Key_Alt
        && e->key() != Qt::Key_Shift)
     {
-    textCursor.setPosition(this->commandEnd());
-    this->setTextCursor(textCursor);
-    message_output_area = false;
-    history_area = false;
+    text_cursor.setPosition(this->commandEnd());
+    this->setTextCursor(text_cursor);
     }
 
   // Start of line should be the start of interactive area
@@ -438,15 +443,15 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
   QTextCursor::MoveMode moveMode = QTextCursor::MoveAnchor;
   if(isMoveLeftWithinLine(e, moveOperation, moveMode))
     {
-    textCursor.movePosition(moveOperation, moveMode);
-    if (textCursor.position() >= this->InteractivePosition)
+    text_cursor.movePosition(moveOperation, moveMode);
+    if (text_cursor.position() >= this->InteractivePosition)
       {
       this->Superclass::keyPressEvent(e);
       }
     else
       {
-      textCursor.setPosition(this->InteractivePosition, moveMode);
-      this->setTextCursor(textCursor);
+      text_cursor.setPosition(this->InteractivePosition, moveMode);
+      this->setTextCursor(text_cursor);
       e->accept();
       }
     this->updateCompleterIfVisible();
@@ -458,15 +463,15 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
   moveMode = QTextCursor::MoveAnchor;
   if(isMoveRighttWithinLine(e, moveOperation, moveMode))
     {
-    textCursor.movePosition(moveOperation, moveMode);
-    if (textCursor.position() <= this->commandEnd())
+    text_cursor.movePosition(moveOperation, moveMode);
+    if (text_cursor.position() <= this->commandEnd())
       {
       this->Superclass::keyPressEvent(e);
       }
     else
       {
-      textCursor.setPosition(this->commandEnd(), moveMode);
-      this->setTextCursor(textCursor);
+      text_cursor.setPosition(this->commandEnd(), moveMode);
+      this->setTextCursor(text_cursor);
       e->accept();
       }
     this->updateCompleterIfVisible();
@@ -479,8 +484,8 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
     // Can delete only if we are not at the end of the command line.
     // There is an exception if something (in the interactive area only) is selected,
     // because it will erase the text selected instead.
-    if (textCursor.position() < this->commandEnd()
-        || (textCursor.position() <= this->commandEnd()
+    if (text_cursor.position() < this->commandEnd()
+        || (text_cursor.position() <= this->commandEnd()
              && selection && !message_output_area && !history_area))
       {
       this->Superclass::keyPressEvent(e);
@@ -497,8 +502,8 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
     // Can delete with backspace only if the cursor is after the InteractivePosition.
     // There is an exception if something (in the interactive area only) is selected,
     // because it will erase the text selected instead.
-    if (textCursor.position() > this->InteractivePosition
-        || (textCursor.position() >= this->InteractivePosition
+    if (text_cursor.position() > this->InteractivePosition
+        || (text_cursor.position() >= this->InteractivePosition
              && selection  && !message_output_area && !history_area))
       {
       this->Superclass::keyPressEvent(e);
@@ -511,7 +516,7 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
   if (e == QKeySequence::DeleteStartOfWord)
       {
       e->accept();
-      if (textCursor.position() > this->InteractivePosition)
+      if (text_cursor.position() > this->InteractivePosition)
         {
         this->Superclass::keyPressEvent(e);
         this->updateCommandBuffer();
@@ -548,8 +553,8 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
   if (e == QKeySequence::InsertParagraphSeparator)
     {
     e->accept();
-    textCursor.setPosition(this->documentEnd());
-    this->setTextCursor(textCursor);
+    text_cursor.setPosition(this->documentEnd());
+    this->setTextCursor(text_cursor);
     if (this->InputEventLoop.isNull())
       {
       this->internalExecuteCommand();
@@ -561,7 +566,7 @@ void ctkConsolePrivate::keyPressEvent(QKeyEvent* e)
     return;
     }
 
-  if (this->CompleterShortcuts.contains(e->key() + e->modifiers()))
+  if (this->CompleterShortcuts.contains(e->key() + static_cast<int>(e->modifiers())))
     {
     e->accept();
     this->updateCompleter();
@@ -696,14 +701,14 @@ void ctkConsolePrivate::updateCompleter()
     {
     // Get the text between the current cursor position
     // and the start of the line
-    QTextCursor textCursor = this->textCursor();
-    while (!textCursor.selectedText().contains(q_ptr->ps1()))
+    QTextCursor text_cursor = this->textCursor();
+    while (!text_cursor.selectedText().contains(q_ptr->ps1()))
       {
-      textCursor.movePosition(QTextCursor::Left, QTextCursor::KeepAnchor);
+      text_cursor.movePosition(QTextCursor::Left, QTextCursor::KeepAnchor);
       }
 
     // search through the text the multiline statement symbol "... " + 1 char (go to the line char)
-    QString commandText = textCursor.selectedText();
+    QString commandText = text_cursor.selectedText();
     int pos_Ps2 = commandText.indexOf(q_ptr->ps2())-1;
     while (pos_Ps2 > -1)
       {
@@ -730,9 +735,9 @@ void ctkConsolePrivate::updateCompleter()
     int savedCursorPosition = this->textCursor().position();
 
     //move the cursor at the end in case of a message displayed
-    textCursor = this->textCursor();
-    textCursor.setPosition(this->documentEnd());
-    this->setTextCursor(textCursor);
+    QTextCursor tc = this->textCursor();
+    tc.setPosition(this->documentEnd());
+    this->setTextCursor(tc);
     // Save color of displayed message
     QColor savedOutputTextColor = this->OutputTextColor;
     QColor savedErrorTextColor = this->ErrorTextColor;
@@ -749,7 +754,7 @@ void ctkConsolePrivate::updateCompleter()
 
     // Restore positions
     this->InteractivePosition = savedInteractivePosition;
-    textCursor = this->textCursor();
+    QTextCursor textCursor = this->textCursor();
     textCursor.setPosition(savedCursorPosition);
     this->setTextCursor(textCursor);
 
@@ -759,9 +764,9 @@ void ctkConsolePrivate::updateCompleter()
       {
       // Get a QRect for the cursor at the start of the
       // current word and then translate it down 8 pixels.
-      textCursor = this->textCursor();
-      textCursor.movePosition(QTextCursor::StartOfWord);
-      QRect cr = this->cursorRect(textCursor);
+      text_cursor = this->textCursor();
+      text_cursor.movePosition(QTextCursor::StartOfWord);
+      QRect cr = this->cursorRect(text_cursor);
       cr.translate(0,8);
       cr.setWidth(this->Completer->popup()->sizeHintForColumn(0)
         + this->Completer->popup()->verticalScrollBar()->sizeHint().width());
@@ -842,12 +847,22 @@ void ctkConsolePrivate::internalExecuteCommand()
   if (this->EditorHints & ctkConsole::AutomaticIndentation)
     {
     QRegExp regExp("^(\\s+)");
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+    if( command.indexOf(regExp) >= 0)
+      {
+      QStringList captured = regExp.namedCaptureGroups();
+      if (captured.size() >= 2)
+        {
+        indent = captured[1];
+        }
+      }
+#else
     if (regExp.indexIn(command) != -1)
       {
       indent = regExp.cap(1);
       }
+#endif
     }
-
   // Give a chance for log messages to appear before displaying the new prompt.
   qApp->processEvents(QEventLoop::ExcludeUserInputEvents);
 
@@ -866,9 +881,9 @@ void ctkConsolePrivate::processInput()
     this->commandBuffer() = command; // Update buffer
     }
 
-  QTextCursor textCursor = this->textCursor();
-  textCursor.movePosition(QTextCursor::End);
-  textCursor.insertText("\n");
+  QTextCursor c(this->document());
+  c.movePosition(QTextCursor::End);
+  c.insertText("\n");
 
   this->InteractivePosition = this->documentEnd();
 
@@ -878,9 +893,8 @@ void ctkConsolePrivate::processInput()
 //-----------------------------------------------------------------------------
 void ctkConsolePrivate::printString(const QString& text)
 {
-  QTextCursor textCursor = this->textCursor();
-  textCursor.movePosition(QTextCursor::End);
-  textCursor.insertText(text);
+  this->textCursor().movePosition(QTextCursor::End);
+  this->textCursor().insertText(text);
 }
 
 //-----------------------------------------------------------------------------
@@ -914,14 +928,14 @@ void ctkConsolePrivate::promptForInput(const QString& indent)
 //-----------------------------------------------------------------------------
 void ctkConsolePrivate::prompt(const QString& text)
 {
-  QTextCursor textCursor = this->textCursor();
+  QTextCursor text_cursor = this->textCursor();
 
   // If the cursor is currently on a clean line, do nothing, otherwise we move
   // the cursor to a new line before showing the prompt.
-  textCursor.movePosition(QTextCursor::StartOfLine);
-  int startpos = textCursor.position();
-  textCursor.movePosition(QTextCursor::EndOfLine);
-  int endpos = textCursor.position();
+  text_cursor.movePosition(QTextCursor::StartOfLine);
+  int startpos = text_cursor.position();
+  text_cursor.movePosition(QTextCursor::EndOfLine);
+  int endpos = text_cursor.position();
   if (endpos != startpos)
     {
     this->textCursor().insertText("\n");
@@ -945,53 +959,51 @@ void ctkConsolePrivate::printWelcomeMessage()
 void ctkConsolePrivate::insertCompletion(const QString& completion)
 {
   Q_Q(ctkConsole);
-  QTextCursor textCursor = this->textCursor();
-  textCursor.setPosition(this->commandEnd());
+  QTextCursor tc = this->textCursor();
   // save the initial cursor position
   QTextCursor endOfCompletion = this->textCursor();
-  endOfCompletion.setPosition(this->commandEnd());
+  endOfCompletion.setPosition(tc.position());
   // Select the previous character
-  textCursor.movePosition(QTextCursor::Left, QTextCursor::KeepAnchor);
-  QString charBeforeCompletion = textCursor.selectedText();
-  if (charBeforeCompletion == ".")
+  tc.movePosition(QTextCursor::Left, QTextCursor::KeepAnchor);
+  if (tc.selectedText()==".")
     {
-    textCursor.insertText(QString(".") + completion);
+    tc.insertText(QString(".") + completion);
     }
   else
     {
     //can't more autocomplete when cursor right after '(' or ')'
-    if (charBeforeCompletion == ")" || charBeforeCompletion == "(")
+    if (tc.selectedText()==")" || tc.selectedText()=="(")
       {
       return;
       }
-    textCursor.clearSelection();
-    textCursor.movePosition(QTextCursor::StartOfWord, QTextCursor::MoveAnchor);
+    tc.clearSelection();
+    tc.movePosition(QTextCursor::StartOfWord, QTextCursor::MoveAnchor);
     if (insertCompletionMethod)
       {
-      textCursor.movePosition(QTextCursor::EndOfWord, QTextCursor::KeepAnchor);
+      tc.movePosition(QTextCursor::EndOfWord, QTextCursor::KeepAnchor);
       }
     else
       {
-      textCursor.setPosition(endOfCompletion.position(), QTextCursor::KeepAnchor);
+      tc.setPosition(endOfCompletion.position(), QTextCursor::KeepAnchor);
       }
-    textCursor.insertText(completion);
-    endOfCompletion.setPosition(textCursor.position());
-    this->setTextCursor(textCursor);
+    tc.insertText(completion);
+    endOfCompletion.setPosition(tc.position());
+    this->setTextCursor(tc);
     }
 
   // Get back the whole command line to apply a cursor offset
   // (moving cursor between parenthsesis if the completion is
   // a callable object with more than the self argument)
   // StartOfBlock don't catch the whole command line if multi-line statement
-  textCursor.movePosition(QTextCursor::StartOfBlock,QTextCursor::KeepAnchor);
-  QString shellLine = textCursor.selectedText();
+  tc.movePosition(QTextCursor::StartOfBlock,QTextCursor::KeepAnchor);
+  QString shellLine = tc.selectedText();
   shellLine.replace(q->ps1(), "");
   shellLine.replace(q->ps2(), "");
-  textCursor.setPosition(endOfCompletion.position());
-  this->setTextCursor(textCursor);
+  tc.setPosition(endOfCompletion.position());
+  this->setTextCursor(tc);
   int cursorOffset = this->Completer->cursorOffset(shellLine);
-  textCursor.movePosition(QTextCursor::Left, QTextCursor::MoveAnchor, cursorOffset);
-  this->setTextCursor(textCursor);
+  tc.movePosition(QTextCursor::Left, QTextCursor::MoveAnchor, cursorOffset);
+  this->setTextCursor(tc);
   this->updateCommandBuffer();
 }
 
@@ -1065,12 +1077,8 @@ void ctkConsolePrivate::pasteText(const QString& text)
       && text.trimmed().contains("\n"))
     {
     // Execute at once
-    q->printMessage("\n" + text.trimmed(), this->StdinTextColor);
+    q->printMessage("\n" + text.trimmed() + "\n", this->StdinTextColor);
     q->executeString(text);
-
-    // Give a chance for log messages to appear before displaying the new prompt.
-    qApp->processEvents(QEventLoop::ExcludeUserInputEvents);
-
     this->promptForInput();
     return;
     }
@@ -1173,10 +1181,10 @@ void ctkConsole::setShellFont(const QFont& font)
   int savedPosition = d->textCursor().position();
   d->selectAll();
   d->setCurrentFont(font);
-  QTextCursor textCursor = d->textCursor();
-  textCursor.clearSelection();
-  textCursor.setPosition(savedPosition);
-  d->setTextCursor(textCursor);
+  QTextCursor tc = d->textCursor();
+  tc.clearSelection();
+  tc.setPosition(savedPosition);
+  d->setTextCursor(tc);
 }
 
 //-----------------------------------------------------------------------------
@@ -1266,10 +1274,10 @@ int ctkConsole::cursorColumn() const
 int ctkConsole::cursorLine() const
 {
   Q_D(const ctkConsole);
-  QTextCursor textCursor = d->textCursor();
-  textCursor.movePosition(QTextCursor::StartOfLine);
+  QTextCursor cursor = d->textCursor();
+  cursor.movePosition(QTextCursor::StartOfLine);
   int lines = 1;
-  QTextBlock block = textCursor.block().previous();
+  QTextBlock block = cursor.block().previous();
   while(block.isValid())
     {
     lines += block.lineCount();
@@ -1384,9 +1392,6 @@ void ctkConsole::runFile(const QString& filePath)
   this->printMessage("\n" + commands.trimmed() + "\n", d->StdinTextColor);
   this->executeString(commands);
 
-  // Give a chance for log messages to appear before displaying the new prompt.
-  qApp->processEvents(QEventLoop::ExcludeUserInputEvents);
-
   // Display a new command prompt and allow the user to resume typing the command.
   d->promptForInput();
   d->replaceCommandBuffer(savedCommand);
@@ -1432,15 +1437,10 @@ void ctkConsole::printMessage(const QString& message, const QColor& color)
 {
   Q_D(ctkConsole);
 
-  // Jump to the end and print text with the selected color
-
-  QTextCursor textCursor = d->textCursor();
-  textCursor.movePosition(QTextCursor::End);
-
   QTextCharFormat format = this->getFormat();
   format.setForeground(color);
-
-  textCursor.insertText(message, format);
+  this->setFormat(format);
+  d->printString(message);
 }
 
 //----------------------------------------------------------------------------
diff --git a/Libs/Widgets/ctkDoubleSpinBox.cpp b/Libs/Widgets/ctkDoubleSpinBox.cpp
index a2f6afd8f5..19b4034171 100644
--- a/Libs/Widgets/ctkDoubleSpinBox.cpp
+++ b/Libs/Widgets/ctkDoubleSpinBox.cpp
@@ -398,13 +398,18 @@ ::validateAndInterpret(QString &input, int &pos,
   // could be because of group separators:
   if (!ok && state == QValidator::Acceptable)
     {
-    if (q->locale().groupSeparator().isPrint())
+    #if (QT_VERSION >= QT_VERSION_CHECK(6,0,0))
+    QChar groupSeparator(q->locale().groupSeparator()[0]);
+    #else
+    QChar groupSeparator(q->locale().groupSeparator());
+    #endif
+    if (groupSeparator.isPrint())
       {
       int start = (dec == -1 ? text.size() : dec)- 1;
       int lastGroupSeparator = start;
       for (int digit = start; digit >= 0; --digit)
         {
-        if (text.at(digit) == q->locale().groupSeparator())
+        if (text.at(digit) == groupSeparator)
           {
           if (digit != lastGroupSeparator - 3)
             {
@@ -1102,7 +1107,10 @@ QSize ctkDoubleSpinBox::sizeHint() const
   opt.rect = this->rect();
   d->CachedSizeHint = this->style()->sizeFromContents(
     QStyle::CT_SpinBox, &opt, newSizeHint, this)
-    .expandedTo(QApplication::globalStrut());
+      #if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+        .expandedTo(QApplication::globalStrut())
+      #endif
+      ;
   return d->CachedSizeHint;
 }
 
@@ -1158,7 +1166,10 @@ QSize ctkDoubleSpinBox::minimumSizeHint() const
   opt.rect = this->rect();
   d->CachedMinimumSizeHint = this->style()->sizeFromContents(
     QStyle::CT_SpinBox, &opt, newSizeHint, this)
-    .expandedTo(QApplication::globalStrut());
+      #if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+        .expandedTo(QApplication::globalStrut())
+      #endif
+      ;
   return d->CachedMinimumSizeHint;
 }
 
diff --git a/Libs/Widgets/ctkExpandButton.cpp b/Libs/Widgets/ctkExpandButton.cpp
index 7eea69c9cd..cf33c306b1 100644
--- a/Libs/Widgets/ctkExpandButton.cpp
+++ b/Libs/Widgets/ctkExpandButton.cpp
@@ -102,7 +102,11 @@ void ctkExpandButton::setOrientation(Qt::Orientation newOrientation)
 {
   Q_D(ctkExpandButton);
   QStyleOption opt;
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   opt.init(this);
+#else
+  opt.initFrom(this);
+#endif
   if(newOrientation == Qt::Horizontal)
     {
     d->defaultPixmap = this->style()->standardPixmap(
diff --git a/Libs/Widgets/ctkMenuButton.cpp b/Libs/Widgets/ctkMenuButton.cpp
index 2216ec3604..33edcd1d30 100644
--- a/Libs/Widgets/ctkMenuButton.cpp
+++ b/Libs/Widgets/ctkMenuButton.cpp
@@ -21,7 +21,6 @@
 // Qt includes
 #include <QApplication>
 #include <QDebug>
-#include <QDesktopWidget>
 #include <QLayout>
 #include <QMouseEvent>
 #include <QMenu>
@@ -159,7 +158,11 @@ void ctkMenuButton::paintEvent(QPaintEvent * _event)
                    QPoint(downArrowRect.left(), downArrowRect.bottom() - borderSize));
   // Draw arrow
   QStyleOption indicatorOpt;
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   indicatorOpt.init(this);
+#else
+  indicatorOpt.initFrom(this);
+#endif
   indicatorOpt.rect = downArrowRect.adjusted(borderSize, borderSize, -borderSize, -borderSize);
   painter.drawPrimitive(QStyle::PE_IndicatorArrowDown, indicatorOpt);
 
diff --git a/Libs/Widgets/ctkPathLineEdit.cpp b/Libs/Widgets/ctkPathLineEdit.cpp
index af0d347f19..1462eabdc5 100644
--- a/Libs/Widgets/ctkPathLineEdit.cpp
+++ b/Libs/Widgets/ctkPathLineEdit.cpp
@@ -29,7 +29,12 @@
 #include <QHBoxLayout>
 #include <QLineEdit>
 #include <QRegExp>
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
 #include <QRegExpValidator>
+#else
+#include <QRegularExpressionValidator>
+#define QRegExpValidator QRegularExpressionValidator
+#endif
 #include <QSettings>
 #include <QStyleOptionComboBox>
 #include <QToolButton>
@@ -462,7 +467,11 @@ QSize ctkPathLineEditPrivate::recomputeSizeHint(QSize& sh)const
     sh.rwidth() = frame + textWidth + browseWidth;
     sh.rheight() = height;
   }
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   return sh.expandedTo(QApplication::globalStrut());
+#else
+  return sh;
+#endif
 }
 
 //-----------------------------------------------------------------------------
@@ -471,7 +480,11 @@ void ctkPathLineEditPrivate::updateFilter()
   Q_Q(ctkPathLineEdit);
   this->Completer->setShowFiles(this->Filters & QDir::Files);
   this->Completer->setNameFilters(ctk::nameFiltersToExtensions(this->NameFilters));
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   this->Validator->setRegExp(ctk::nameFiltersToRegExp(this->NameFilters));
+#else
+  this->Validator->setRegularExpression(ctk::nameFiltersToRegExp(this->NameFilters));
+#endif
 }
 
 //-----------------------------------------------------------------------------
diff --git a/Libs/Widgets/ctkPathListButtonsWidget.cpp b/Libs/Widgets/ctkPathListButtonsWidget.cpp
index be5f240b2c..502c09f89f 100644
--- a/Libs/Widgets/ctkPathListButtonsWidget.cpp
+++ b/Libs/Widgets/ctkPathListButtonsWidget.cpp
@@ -157,7 +157,11 @@ QStringList ctkPathListButtonsWidgetPrivate::openAddFilesDialog(bool multiple)
   }
 
   QFileDialog fileDialog(q, caption);
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   fileDialog.setReadOnly(true);
+#else
+  fileDialog.setOption(QFileDialog::Option::ReadOnly, true);
+#endif  
 
   if (multiple)
   {
diff --git a/Libs/Widgets/ctkPixmapIconEngine.cpp b/Libs/Widgets/ctkPixmapIconEngine.cpp
index cb050f5e71..c605164363 100644
--- a/Libs/Widgets/ctkPixmapIconEngine.cpp
+++ b/Libs/Widgets/ctkPixmapIconEngine.cpp
@@ -335,6 +335,9 @@ bool ctkPixmapIconEngine::write(QDataStream &out) const
 
 void ctkPixmapIconEngine::virtual_hook(int id, void *data)
 {
+#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+    return QIconEngine::virtual_hook(id, data);
+#else
   switch (id) {
 #if QT_VERSION >= QT_VERSION_CHECK(5,0,0)
     case QIconEngine::AvailableSizesHook: {
@@ -364,4 +367,5 @@ void ctkPixmapIconEngine::virtual_hook(int id, void *data)
       QIconEngineV2::virtual_hook(id, data);
 #endif
     }
+#endif
 }
diff --git a/Libs/Widgets/ctkPopupWidget.cpp b/Libs/Widgets/ctkPopupWidget.cpp
index 1015547f12..b01662549f 100644
--- a/Libs/Widgets/ctkPopupWidget.cpp
+++ b/Libs/Widgets/ctkPopupWidget.cpp
@@ -20,7 +20,9 @@
 
 // Qt includes
 #include <QApplication>
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
 #include <QDesktopWidget>
+#endif
 #include <QDialog>
 #include <QDir>
 #include <QEvent>
@@ -416,7 +418,11 @@ void ctkPopupWidget::leaveEvent(QEvent* event)
 }
 
 // --------------------------------------------------------------------------
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+void ctkPopupWidget::enterEvent(QEnterEvent* event)
+#else
 void ctkPopupWidget::enterEvent(QEvent* event)
+#endif
 {
   Q_D(ctkPopupWidget);
   QTimer::singleShot(d->ShowDelay, this, SLOT(updatePopup()));
diff --git a/Libs/Widgets/ctkPopupWidget.h b/Libs/Widgets/ctkPopupWidget.h
index 7922828f12..c5f7f25cf1 100644
--- a/Libs/Widgets/ctkPopupWidget.h
+++ b/Libs/Widgets/ctkPopupWidget.h
@@ -113,7 +113,11 @@ public Q_SLOTS:
 
 protected:
   virtual void leaveEvent(QEvent* event);
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+  virtual void enterEvent(QEnterEvent* event);
+#else
   virtual void enterEvent(QEvent* event);
+#endif
   virtual bool eventFilter(QObject* obj, QEvent* event);
 
   /// Widget the popup is attached to. It opens right under \a baseWidget
diff --git a/Libs/Widgets/ctkPushButton.cpp b/Libs/Widgets/ctkPushButton.cpp
index 82956dc49a..4c5179c536 100644
--- a/Libs/Widgets/ctkPushButton.cpp
+++ b/Libs/Widgets/ctkPushButton.cpp
@@ -59,7 +59,6 @@ QRect ctkPushButtonPrivate::iconRect()const
 
   QSize iconSize = q->iconSize();
   int buttonHeight = opt.rect.height();
-  int buttonWidth = opt.rect.width();
   uint tf = this->ButtonTextAlignment;
   if (q->style()->styleHint(QStyle::SH_UnderlineShortcut, &opt, q))
     {
@@ -150,8 +149,11 @@ QSize ctkPushButtonPrivate::buttonSizeHint(bool computeMinimum)const
     }
   h = qMax(h, sz.height());
   //opt.rect.setSize(QSize(w, h)); // PM_MenuButtonIndicator depends on the height
-  QSize buttonSize = (q->style()->sizeFromContents(QStyle::CT_PushButton, &opt, QSize(w, h), q).
-                      expandedTo(QApplication::globalStrut()));
+  QSize buttonSize = q->style()->sizeFromContents(QStyle::CT_PushButton, &opt, QSize(w, h), q)
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
+                      .expandedTo(QApplication::globalStrut())
+#endif
+                      ;
   return buttonSize;
 }
 
@@ -160,7 +162,11 @@ QStyleOptionButton ctkPushButtonPrivate::drawIcon(QPainter* p)
 {
   Q_Q(ctkPushButton);
   QStyleOptionButton iconOpt;
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
   iconOpt.init(q);
+#else
+  iconOpt.initFrom(q);
+#endif
   iconOpt.rect = this->iconRect();
   if (q->icon().isNull())
     {
diff --git a/Libs/Widgets/ctkQImageView.cpp b/Libs/Widgets/ctkQImageView.cpp
index fb2b907124..0798b1c9d2 100644
--- a/Libs/Widgets/ctkQImageView.cpp
+++ b/Libs/Widgets/ctkQImageView.cpp
@@ -738,7 +738,11 @@ void ctkQImageView::mousePressEvent( QMouseEvent * event )
         d->MouseLastIntensityLevel = this->intensityLevel();
         break;
         }
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
       case Qt::MidButton:
+#else
+      case Qt::MiddleButton:
+#endif
         {
         d->MouseMiddleDragging = true;
         d->MouseLastX = event->x();
diff --git a/Libs/Widgets/ctkRangeSlider.cpp b/Libs/Widgets/ctkRangeSlider.cpp
index a20a99b242..48fd0b9038 100644
--- a/Libs/Widgets/ctkRangeSlider.cpp
+++ b/Libs/Widgets/ctkRangeSlider.cpp
@@ -111,7 +111,7 @@ ctkRangeSliderPrivate::ctkRangeSliderPrivate(ctkRangeSlider& object)
   this->m_SubclassClickOffset = 0;
   this->m_SubclassPosition = 0;
   this->m_SubclassWidth = 0.0;
-  this->m_SelectedHandles = 0;
+  this->m_SelectedHandles = ctkRangeSliderPrivate::Handles(); // initialize QFlags with no flags 
   this->m_SymmetricMoves = false;
 }
 
@@ -773,7 +773,7 @@ void ctkRangeSlider::mouseReleaseEvent(QMouseEvent* mouseEvent)
   this->QSlider::mouseReleaseEvent(mouseEvent);
 
   setSliderDown(false);
-  d->m_SelectedHandles = 0;
+  d->m_SelectedHandles = ctkRangeSliderPrivate::Handles(); // initialize QFlags with no flags set
 
   this->update();
 }
diff --git a/Libs/Widgets/ctkScreenshotDialog.cpp b/Libs/Widgets/ctkScreenshotDialog.cpp
index 6838bf77b3..3c90a4e74d 100644
--- a/Libs/Widgets/ctkScreenshotDialog.cpp
+++ b/Libs/Widgets/ctkScreenshotDialog.cpp
@@ -169,7 +169,7 @@ void ctkScreenshotDialogPrivate::lockAspectRatio(bool lock)
       }
     else
       {
-      QString message = QString("Height of widget: ") + curSize.height() +\
+      QString message = QString("Height of widget: ") + QString::number(curSize.height()) +\
         QString(" is invalid. Check widget dimensions. Using default aspect\
           ratio (1.0).");
       QMessageBox::warning(q, "Invalid widget dimensions", message,
@@ -191,7 +191,7 @@ void ctkScreenshotDialogPrivate::onWidthEdited()
       }
     else
       {
-      QString message = QString("Aspect ratio: ") + this->AspectRatio +\
+      QString message = QString("Aspect ratio: ") + QString::number(this->AspectRatio) +\
         QString(" is invalid. Check widget dimensions.");
       QMessageBox::warning(q, "Invalid aspect ratio", message, QMessageBox::Ok);
       }
diff --git a/Libs/Widgets/ctkSettings.cpp b/Libs/Widgets/ctkSettings.cpp
index 67f76598fa..d605118713 100644
--- a/Libs/Widgets/ctkSettings.cpp
+++ b/Libs/Widgets/ctkSettings.cpp
@@ -53,8 +53,12 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 // Qt includes
 #include <QDialog>
 #include <QMainWindow>
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
 #include <QDesktopWidget>
-
+#else
+#include <QGuiApplication>
+#include <QScreen>
+#endif
 //-----------------------------------------------------------------------------
 ctkSettings::ctkSettings(const QString& organization,
                          const QString& application,
@@ -134,8 +138,12 @@ void ctkSettings::restoreState(const QString& key, QMainWindow& window)
     QPoint windowTopLeft = this->value("Position").toPoint();
     QRect mwRect(windowTopLeft, window.size());
     
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
     QDesktopWidget desktop;
     QRect desktopRect = desktop.availableGeometry( desktop.primaryScreen() );
+#else
+    QRect desktopRect = QGuiApplication::primaryScreen()->availableGeometry();
+#endif
     // try moving it to keep size
     if(!desktopRect.contains(mwRect))
       {
diff --git a/Libs/Widgets/ctkSettingsDialog.cpp b/Libs/Widgets/ctkSettingsDialog.cpp
index ea0a767e3d..3d74f68ce6 100644
--- a/Libs/Widgets/ctkSettingsDialog.cpp
+++ b/Libs/Widgets/ctkSettingsDialog.cpp
@@ -25,6 +25,9 @@
 #include <QPushButton>
 #include <QSettings>
 
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+#define QRegExp QRegularExpression
+#endif
 // CTK includes
 #include "ctkSettingsPanel.h"
 #include "ctkSettingsDialog.h"
diff --git a/Libs/Widgets/ctkSettingsDialog.h b/Libs/Widgets/ctkSettingsDialog.h
index 2bad72f315..7edbfadd6d 100644
--- a/Libs/Widgets/ctkSettingsDialog.h
+++ b/Libs/Widgets/ctkSettingsDialog.h
@@ -26,12 +26,18 @@
 
 // CTK includes
 #include "ctkWidgetsExport.h"
-
+#if CTK_COMPILING_FROM_MOC_CPP
+#include <QAbstractButton>
+#include <QSettings>
+#include <QTreeWidgetItem>
+#include "ctkSettingsPanel.h"
+#else
 class QAbstractButton;
 class QSettings;
 class QTreeWidgetItem;
-class ctkSettingsDialogPrivate;
 class ctkSettingsPanel;
+#endif
+class ctkSettingsDialogPrivate;
 
 /// \ingroup Widgets
 class CTK_WIDGETS_EXPORT ctkSettingsDialog : public QDialog
diff --git a/Libs/Widgets/ctkSettingsPanel.h b/Libs/Widgets/ctkSettingsPanel.h
index 3916ce5daa..6b6dc60ab3 100644
--- a/Libs/Widgets/ctkSettingsPanel.h
+++ b/Libs/Widgets/ctkSettingsPanel.h
@@ -27,8 +27,11 @@
 
 // CTK includes
 #include "ctkWidgetsExport.h"
-
+#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#include <QSettings>
+#else
 class QSettings;
+#endif
 class ctkSettingsPanelPrivate;
 
 /// \ingroup Widgets
diff --git a/Libs/Widgets/ctkSizeGrip.cpp b/Libs/Widgets/ctkSizeGrip.cpp
index 886d53ba0e..f80470e0d3 100644
--- a/Libs/Widgets/ctkSizeGrip.cpp
+++ b/Libs/Widgets/ctkSizeGrip.cpp
@@ -223,9 +223,14 @@ QSize ctkSizeGrip::sizeHint() const
       break;
     };
   QStyleOption opt(0);
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   opt.init(this);
-  return (this->style()->sizeFromContents(contents, &opt, minSize, this).
-          expandedTo(QApplication::globalStrut()));
+  return this->style()->sizeFromContents(contents, &opt, minSize, this).expandedTo(QApplication::globalStrut());
+#else
+  opt.initFrom(this);
+  return this->style()->sizeFromContents(contents, &opt, minSize, this);
+#endif
+         
 }
 
 //------------------------------------------------------------------------------
@@ -262,7 +267,11 @@ void ctkSizeGrip::paintEvent(QPaintEvent *event)
     default:
       {
       QStyleOptionSizeGrip opt;
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
       opt.init(this);
+#else
+      opt.initFrom(this);
+#endif
       opt.corner = this->isLeftToRight() ? Qt::BottomRightCorner : Qt::BottomLeftCorner;
       style()->drawControl(QStyle::CE_SizeGrip, &opt, &painter, this);
       break;
@@ -356,9 +365,9 @@ void ctkSizeGrip::mouseMoveEvent(QMouseEvent * e)
       widgetSizeHint.rheight() = d->WidgetToResize->heightForWidth(widgetSizeHint.width());
       }
     }
-
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   widgetSizeHint = widgetSizeHint.expandedTo(QApplication::globalStrut());
-
+#endif
   this->setWidgetSizeHint(
     QSize(d->Orientations & Qt::Horizontal ? widgetSizeHint.width() : -1,
           d->Orientations & Qt::Vertical ? widgetSizeHint.height() : -1));
diff --git a/Libs/Widgets/ctkThumbnailLabel.cpp b/Libs/Widgets/ctkThumbnailLabel.cpp
index 71879d211a..1106efbc45 100644
--- a/Libs/Widgets/ctkThumbnailLabel.cpp
+++ b/Libs/Widgets/ctkThumbnailLabel.cpp
@@ -292,7 +292,11 @@ QSize ctkThumbnailLabel::sizeHint()const
   Q_D(const ctkThumbnailLabel);
   return d->OriginalThumbnail.isNull() ?
     this->Superclass::sizeHint() :
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
     d->OriginalThumbnail.size().expandedTo(QApplication::globalStrut());
+#else
+    d->OriginalThumbnail.size();
+#endif
 }
 
 //----------------------------------------------------------------------------
diff --git a/Libs/Widgets/ctkTransferFunctionView.cpp b/Libs/Widgets/ctkTransferFunctionView.cpp
index 695a879d06..4ec0b8585c 100644
--- a/Libs/Widgets/ctkTransferFunctionView.cpp
+++ b/Libs/Widgets/ctkTransferFunctionView.cpp
@@ -90,12 +90,21 @@ void ctkTransferFunctionView::resizeEvent(QResizeEvent * event)
       }
     }
   */
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   QMatrix zoomMatrix;
   zoomMatrix.scale(event->size().width(), event->size().height());
   bool blocked = this->blockSignals(true);
   this->setMatrix(zoomMatrix);
   this->blockSignals(blocked);
+#else
+  QTransform zoomMatrix;
+  zoomMatrix.scale(event->size().width(), event->size().height());
+  bool blocked = this->blockSignals(true);
+  this->setTransform(zoomMatrix);
+  this->blockSignals(blocked);
+#endif
   this->QGraphicsView::resizeEvent(event);
+
   // Control points are resized by the view transform, we want
   // fixed size control points, lines...
   //this->fitInView(this->scene()->sceneRect());
diff --git a/Libs/Widgets/ctkTreeComboBox.cpp b/Libs/Widgets/ctkTreeComboBox.cpp
index c5ece5c6d5..5448a7f67c 100644
--- a/Libs/Widgets/ctkTreeComboBox.cpp
+++ b/Libs/Widgets/ctkTreeComboBox.cpp
@@ -20,12 +20,18 @@
 
 // Qt includes
 #include <QApplication>
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
 #include <QDesktopWidget>
+#else
+#include <QScreen>
+#include <QWindow>
+#endif
 #include <QEvent>
 #include <QHeaderView>
 #include <QKeyEvent>
 #include <QLayout>
 #include <QScrollBar>
+
 #if QT_VERSION < QT_VERSION_CHECK(5,0,0)
 # include <QInputContext>
 #endif
@@ -239,8 +245,12 @@ void ctkTreeComboBox::resizePopup()
   this->initStyleOption(&opt);
   QRect listRect(style->subControlRect(QStyle::CC_ComboBox, &opt,
                                        QStyle::SC_ComboBoxListBoxPopup, this));
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
   QRect screen = QApplication::desktop()->availableGeometry(
     QApplication::desktop()->screenNumber(this));
+#else
+  QRect screen = this->windowHandle()->screen()->availableGeometry();
+#endif
   QPoint below = this->mapToGlobal(listRect.bottomLeft());
   int belowHeight = screen.bottom() - below.y();
   QPoint above = this->mapToGlobal(listRect.topLeft());
@@ -291,11 +301,19 @@ void ctkTreeComboBox::resizePopup()
 
       // add the frame of the container
       int marginTop, marginBottom;
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
       container->getContentsMargins(0, &marginTop, 0, &marginBottom);
+#else
+      container->layout()->getContentsMargins(0, &marginTop, 0, &marginBottom);
+#endif
       heightMargin += marginTop + marginBottom;
 
       //add the frame of the view
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
       this->view()->getContentsMargins(0, &marginTop, 0, &marginBottom);
+#else
+      this->view()->layout()->getContentsMargins(0, &marginTop, 0, &marginBottom);
+#endif      
       //marginTop += static_cast<QAbstractScrollAreaPrivate *>(QObjectPrivate::get(this->view()))->top;
       //marginBottom += static_cast<QAbstractScrollAreaPrivate *>(QObjectPrivate::get(this->view()))->bottom;
       heightMargin += marginTop + marginBottom;
diff --git a/Libs/Widgets/ctkWidgetsUtils.cpp b/Libs/Widgets/ctkWidgetsUtils.cpp
index 911a398a0c..d92c1d55d5 100644
--- a/Libs/Widgets/ctkWidgetsUtils.cpp
+++ b/Libs/Widgets/ctkWidgetsUtils.cpp
@@ -21,10 +21,15 @@
 // Qt includes
 #include <QBuffer>
 #include <QImage>
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
 #include <QGLWidget>
+#else
+#include <QOpenGLWidget>
+#define QGLWidget QOpenGLWidget
+#define grabFrameBuffer grabFramebuffer
+#endif
 #include <QPainter>
 #include <QWidget>
-
 // ctkWidgets includes
 #include "ctkWidgetsUtils.h"
 
diff --git a/Libs/Widgets/ctkWorkflowButtonBoxWidget.cpp b/Libs/Widgets/ctkWorkflowButtonBoxWidget.cpp
index df5304a0d2..f3c99e9511 100644
--- a/Libs/Widgets/ctkWorkflowButtonBoxWidget.cpp
+++ b/Libs/Widgets/ctkWorkflowButtonBoxWidget.cpp
@@ -194,10 +194,17 @@ void ctkWorkflowButtonBoxWidgetPrivate::updateGoToButtons(ctkWorkflowStep* curre
   Q_ASSERT(q->layout());
 
   // Change the buttons only if the set of steps to have goTo buttons is either empty or has changed
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
   QSet<ctkWorkflowStep*> goToStepsToHaveButtons =
     QSet<ctkWorkflowStep*>::fromList(this->Workflow->finishSteps());
   QSet<ctkWorkflowStep*> goToStepsThatHaveButtons =
     QSet<ctkWorkflowStep*>::fromList(this->GoToButtonToStepMap.values());
+#else 
+  QList<ctkWorkflowStep*> steps =  this->Workflow->finishSteps();
+  QSet<ctkWorkflowStep*> goToStepsToHaveButtons(steps.begin(), steps.end());
+  steps = this->GoToButtonToStepMap.values();
+  QSet<ctkWorkflowStep*> goToStepsThatHaveButtons(steps.begin(), steps.end());
+#endif
 
   // Remove the buttons if the set of steps to have goTo buttons has changed
   if (goToStepsThatHaveButtons != goToStepsToHaveButtons)
diff --git a/Libs/Widgets/ctkWorkflowWidget.cpp b/Libs/Widgets/ctkWorkflowWidget.cpp
index 0048fe85e3..c7f2292793 100644
--- a/Libs/Widgets/ctkWorkflowWidget.cpp
+++ b/Libs/Widgets/ctkWorkflowWidget.cpp
@@ -33,6 +33,10 @@
 #include "ctkWorkflowButtonBoxWidget.h"
 #include "ctkWorkflowGroupBox.h"
 
+#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#include <QRegExp>
+#endif
+
 // STD includes
 #include <iostream>
 
diff --git a/Libs/XNAT/Core/Testing/CMakeLists.txt b/Libs/XNAT/Core/Testing/CMakeLists.txt
index 9f7c7d6521..a93fb87a09 100644
--- a/Libs/XNAT/Core/Testing/CMakeLists.txt
+++ b/Libs/XNAT/Core/Testing/CMakeLists.txt
@@ -22,7 +22,7 @@ ctk_add_executable_utf8(${KIT}CppTests ${Tests} ${KITTests_SRCS} ${KITTests_MOC_
 target_link_libraries(${KIT}CppTests ${LIBRARY_NAME} ${CTK_BASE_LIBRARIES})
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  target_link_libraries(${KIT}CppTests Qt5::Test)
+  target_link_libraries(${KIT}CppTests Qt${CTK_QT_VERSION}::Test)
 endif()
 
 SIMPLE_TEST(ctkXnatSessionTest)
diff --git a/Libs/XNAT/Widgets/CMakeLists.txt b/Libs/XNAT/Widgets/CMakeLists.txt
index 505f1d9958..878b6256d6 100644
--- a/Libs/XNAT/Widgets/CMakeLists.txt
+++ b/Libs/XNAT/Widgets/CMakeLists.txt
@@ -32,7 +32,7 @@ set(KIT_target_libraries)
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND KIT_target_libraries Qt5::Widgets)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Widgets)
 endif()
 
 ctkMacroBuildLib(
diff --git a/Plugins/org.commontk.dah.core/CMakeLists.txt b/Plugins/org.commontk.dah.core/CMakeLists.txt
index b2577ea4d0..cb9f3dffce 100644
--- a/Plugins/org.commontk.dah.core/CMakeLists.txt
+++ b/Plugins/org.commontk.dah.core/CMakeLists.txt
@@ -48,7 +48,7 @@ set(PLUGIN_resources
 ctkFunctionGetTargetLibraries(PLUGIN_target_libraries)
 
 if(CTK_QT_VERSION VERSION_GREATER "4")
-  list(APPEND PLUGIN_target_libraries Qt5::Network Qt5::Widgets)
+  list(APPEND KIT_target_libraries Qt${CTK_QT_VERSION}::Network Qt${CTK_QT_VERSION}::Widgets)
 endif()
 
 ctkMacroBuildPlugin(