diff --git a/3rdparty/tbb/CMakeLists.txt b/3rdparty/tbb/CMakeLists.txt
index c728440f27eeafe62b1801fa8845489e42823c4c..d460837f84e45a8cd4cbd2a873ec292ea389eff7 100644
--- a/3rdparty/tbb/CMakeLists.txt
+++ b/3rdparty/tbb/CMakeLists.txt
@@ -83,19 +83,7 @@ set(tbb_tarball "${CMAKE_CURRENT_SOURCE_DIR}/${tbb_ver}_src.tgz")
 set(tbb_src_dir "${CMAKE_CURRENT_BINARY_DIR}/${tbb_ver}")
 
 macro(getMD5 filename varname)
-  if(CMAKE_VERSION VERSION_GREATER 2.8.6)
-    file(MD5 "${filename}" ${varname})
-  else()
-    execute_process(COMMAND ${CMAKE_COMMAND} -E md5sum "${filename}"
-              RESULT_VARIABLE getMD5_RESULT
-              OUTPUT_VARIABLE getMD5_OUTPUT
-              OUTPUT_STRIP_TRAILING_WHITESPACE)
-    if(getMD5_RESULT EQUAL 0)
-      string(REGEX MATCH "^[a-z0-9]+" ${varname} "${getMD5_OUTPUT}")
-    else()
-      set(${varname} "invalid_md5")
-    endif()
-  endif()
+  file(MD5 "${filename}" ${varname})
 endmacro()
 
 if(EXISTS "${tbb_tarball}")
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 335ef8a998c9d5ab157ca587e12ee7ee16c21d03..3bd684327be967db45d8f6b5c282d7106dea9eca 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -38,7 +38,7 @@ endif(NOT CMAKE_TOOLCHAIN_FILE)
 
 # must go before the project command
 set(CMAKE_CONFIGURATION_TYPES "Debug;Release" CACHE STRING "Configs" FORCE)
-if(DEFINED CMAKE_BUILD_TYPE AND CMAKE_VERSION VERSION_GREATER "2.8")
+if(DEFINED CMAKE_BUILD_TYPE)
   set_property( CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS ${CMAKE_CONFIGURATION_TYPES} )
 endif()
 
@@ -110,10 +110,10 @@ endif()
 OCV_OPTION(WITH_1394           "Include IEEE1394 support"                    ON   IF (NOT ANDROID AND NOT IOS) )
 OCV_OPTION(WITH_AVFOUNDATION   "Use AVFoundation for Video I/O"              ON   IF IOS)
 OCV_OPTION(WITH_CARBON         "Use Carbon for UI instead of Cocoa"          OFF  IF APPLE )
-OCV_OPTION(WITH_CUDA           "Include NVidia Cuda Runtime support"         ON   IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT ANDROID AND NOT IOS) )
-OCV_OPTION(WITH_CUFFT          "Include NVidia Cuda Fast Fourier Transform (FFT) library support"            ON  IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT ANDROID AND NOT IOS) )
-OCV_OPTION(WITH_CUBLAS         "Include NVidia Cuda Basic Linear Algebra Subprograms (BLAS) library support" OFF IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT ANDROID AND NOT IOS) )
-OCV_OPTION(WITH_NVCUVID        "Include NVidia Video Decoding library support"                               OFF IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT ANDROID AND NOT IOS AND NOT APPLE) )
+OCV_OPTION(WITH_CUDA           "Include NVidia Cuda Runtime support"                                         ON  IF (NOT ANDROID AND NOT IOS) )
+OCV_OPTION(WITH_CUFFT          "Include NVidia Cuda Fast Fourier Transform (FFT) library support"            ON  IF (NOT ANDROID AND NOT IOS) )
+OCV_OPTION(WITH_CUBLAS         "Include NVidia Cuda Basic Linear Algebra Subprograms (BLAS) library support" OFF IF (NOT ANDROID AND NOT IOS) )
+OCV_OPTION(WITH_NVCUVID        "Include NVidia Video Decoding library support"                               OFF IF (NOT ANDROID AND NOT IOS AND NOT APPLE) )
 OCV_OPTION(WITH_EIGEN          "Include Eigen2/Eigen3 support"               ON)
 OCV_OPTION(WITH_VFW            "Include Video for Windows support"           ON   IF WIN32 )
 OCV_OPTION(WITH_FFMPEG         "Include FFMPEG support"                      ON   IF (NOT ANDROID AND NOT IOS))
@@ -184,7 +184,7 @@ OCV_OPTION(INSTALL_TO_MANGLED_PATHS "Enables mangled install paths, that help wi
 # OpenCV build options
 # ===================================================
 OCV_OPTION(ENABLE_PRECOMPILED_HEADERS "Use precompiled headers"                                  ON   IF (NOT IOS) )
-OCV_OPTION(ENABLE_SOLUTION_FOLDERS    "Solution folder in Visual Studio or in other IDEs"        (MSVC_IDE OR CMAKE_GENERATOR MATCHES Xcode) IF (CMAKE_VERSION VERSION_GREATER "2.8.0") )
+OCV_OPTION(ENABLE_SOLUTION_FOLDERS    "Solution folder in Visual Studio or in other IDEs"        (MSVC_IDE OR CMAKE_GENERATOR MATCHES Xcode) )
 OCV_OPTION(ENABLE_PROFILING           "Enable profiling in the GCC compiler (Add flags: -g -pg)" OFF  IF CMAKE_COMPILER_IS_GNUCXX )
 OCV_OPTION(ENABLE_OMIT_FRAME_POINTER  "Enable -fomit-frame-pointer for GCC"                      ON   IF CMAKE_COMPILER_IS_GNUCXX AND NOT (APPLE AND CMAKE_COMPILER_IS_CLANGCXX) )
 OCV_OPTION(ENABLE_POWERPC             "Enable PowerPC for GCC"                                   ON   IF (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_SYSTEM_PROCESSOR MATCHES powerpc.*) )
diff --git a/cmake/OpenCVConfig.cmake b/cmake/OpenCVConfig.cmake
index 300fcd41931a6885dcd03d33dbb1477702b0adbd..8e3708dd3df18e345d4a2302a0d656f82c20dfc1 100644
--- a/cmake/OpenCVConfig.cmake
+++ b/cmake/OpenCVConfig.cmake
@@ -38,11 +38,9 @@
 #      - OpenCV_STATIC
 #      - OpenCV_CUDA
 
-if(CMAKE_VERSION VERSION_GREATER 2.6)
-  get_property(OpenCV_LANGUAGES GLOBAL PROPERTY ENABLED_LANGUAGES)
-  if(NOT ";${OpenCV_LANGUAGES};" MATCHES ";CXX;")
-    enable_language(CXX)
-  endif()
+get_property(OpenCV_LANGUAGES GLOBAL PROPERTY ENABLED_LANGUAGES)
+if(NOT ";${OpenCV_LANGUAGES};" MATCHES ";CXX;")
+  enable_language(CXX)
 endif()
 
 if(NOT DEFINED OpenCV_STATIC)
@@ -92,9 +90,7 @@ elseif(MINGW)
   endif()
 endif()
 
-if(CMAKE_VERSION VERSION_GREATER 2.6.2)
-  unset(OpenCV_CONFIG_PATH CACHE)
-endif()
+unset(OpenCV_CONFIG_PATH CACHE)
 
 get_filename_component(OpenCV_CONFIG_PATH "${CMAKE_CURRENT_LIST_FILE}" PATH CACHE)
 if(OpenCV_RUNTIME AND OpenCV_ARCH)
@@ -156,4 +152,3 @@ else()
   set(OpenCV_FOUND FALSE CACHE BOOL "" FORCE)
   set(OPENCV_FOUND FALSE CACHE BOOL "" FORCE)
 endif()
-
diff --git a/cmake/OpenCVDetectAndroidSDK.cmake b/cmake/OpenCVDetectAndroidSDK.cmake
index ee4188897c2fd9e75571872099bbb6c1b580d89c..68be77619ddc2860fc720a92ece4c0e0d79da2ab 100644
--- a/cmake/OpenCVDetectAndroidSDK.cmake
+++ b/cmake/OpenCVDetectAndroidSDK.cmake
@@ -124,7 +124,7 @@ if(ANDROID_EXECUTABLE)
   if(NOT ANDROID_SDK_TARGET)
     set(ANDROID_SDK_TARGET "" CACHE STRING "Android SDK target for the OpenCV Java API and samples")
   endif()
-  if(ANDROID_SDK_TARGETS AND CMAKE_VERSION VERSION_GREATER "2.8")
+  if(ANDROID_SDK_TARGETS)
     set_property( CACHE ANDROID_SDK_TARGET PROPERTY STRINGS ${ANDROID_SDK_TARGETS} )
   endif()
 endif(ANDROID_EXECUTABLE)
diff --git a/cmake/OpenCVDetectCUDA.cmake b/cmake/OpenCVDetectCUDA.cmake
index 1e561a32efff8b3b4767e124644dd571e256840e..076da108f74b5a22e3685b64d390b7863056229c 100644
--- a/cmake/OpenCVDetectCUDA.cmake
+++ b/cmake/OpenCVDetectCUDA.cmake
@@ -1,8 +1,3 @@
-if(${CMAKE_VERSION} VERSION_LESS "2.8.3")
-  message(STATUS "WITH_CUDA flag requires CMake 2.8.3 or newer. CUDA support is disabled.")
-  return()
-endif()
-
 if(WIN32 AND NOT MSVC)
   message(STATUS "CUDA compilation is disabled (due to only Visual Studio compiler supported on your platform).")
   return()
diff --git a/cmake/OpenCVFindLibsGUI.cmake b/cmake/OpenCVFindLibsGUI.cmake
index 04c77d8ec504ee7f70418c3299cc6a001a7383c9..89982b2622fb9c9178066c5dc2296138cee739d9 100644
--- a/cmake/OpenCVFindLibsGUI.cmake
+++ b/cmake/OpenCVFindLibsGUI.cmake
@@ -15,7 +15,7 @@ endif(WITH_WIN32UI)
 # --- QT4 ---
 ocv_clear_vars(HAVE_QT HAVE_QT5)
 if(WITH_QT)
-  if(NOT CMAKE_VERSION VERSION_LESS 2.8.3 AND NOT WITH_QT EQUAL 4)
+  if(NOT WITH_QT EQUAL 4)
     find_package(Qt5Core)
     find_package(Qt5Gui)
     find_package(Qt5Widgets)
diff --git a/modules/highgui/CMakeLists.txt b/modules/highgui/CMakeLists.txt
index 4a748df55e691c6936061b173264b383277c9b24..dbea6ec1c28d093cc817d84c66242919eddeaf9f 100644
--- a/modules/highgui/CMakeLists.txt
+++ b/modules/highgui/CMakeLists.txt
@@ -293,11 +293,6 @@ if(WIN32 AND WITH_FFMPEG)
   set(ffmpeg_bare_name_ver "opencv_ffmpeg${OPENCV_DLLVERSION}${FFMPEG_SUFFIX}.dll")
   set(ffmpeg_path "${OpenCV_SOURCE_DIR}/3rdparty/ffmpeg/${ffmpeg_bare_name}")
 
-  #if(MSVC AND CMAKE_VERSION VERSION_GREATER "2.8.2")
-  #  add_custom_command(TARGET ${the_module} POST_BUILD
-  #                     COMMAND ${CMAKE_COMMAND} -E copy "${ffmpeg_path}" "${EXECUTABLE_OUTPUT_PATH}/$<CONFIGURATION>/${ffmpeg_bare_name_ver}"
-  #                     COMMENT "Copying ${ffmpeg_path} to the output directory")
-  #else
   if(MSVC_IDE)
     add_custom_command(TARGET ${the_module} POST_BUILD
                        COMMAND ${CMAKE_COMMAND} -E copy "${ffmpeg_path}" "${EXECUTABLE_OUTPUT_PATH}/Release/${ffmpeg_bare_name_ver}"