diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,7 +9,7 @@
 
 PROJECT(${PROJECT_NAME})
 
-SET(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake)
+SET(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)
 
 INCLUDE(FindDoxygen)
 INCLUDE(FindGhostscript)
@@ -38,10 +38,12 @@
 ENABLE_TESTING()
 
 ADD_SUBDIRECTORY(lemon)
-ADD_SUBDIRECTORY(demo)
-ADD_SUBDIRECTORY(tools)
-ADD_SUBDIRECTORY(doc)
-ADD_SUBDIRECTORY(test)
+IF(${CMAKE_SOURCE_DIR} STREQUAL ${PROJECT_SOURCE_DIR})
+  ADD_SUBDIRECTORY(demo)
+  ADD_SUBDIRECTORY(tools)
+  ADD_SUBDIRECTORY(doc)
+  ADD_SUBDIRECTORY(test)
+ENDIF(${CMAKE_SOURCE_DIR} STREQUAL ${PROJECT_SOURCE_DIR})
 
 IF(WIN32)
   SET(CPACK_PACKAGE_NAME ${PROJECT_NAME})