To have my .cpp and .h files a little bit sorted up pending on their responsibilitie I decided to put them into seperate folders I used the following structure: root | -CMakeLists.txt [rootCmakeList] src | -main.cpp …….| ……. math …….| …….-CMakeLists.txt[mathCmakeList] …….-Algebra.h …….-Algebra.cpp …….XML[xmlCmakeList] …….| …….-CMakeLists.txt …….-AwesomeXML.h …….-AwesomeXML.cpp The [rootCmakeList] looks: The [mathCmakeList] looks: The [xmlCmakeList] looks: So far so