diff --git a/CMakeLists.txt b/CMakeLists.txt
index d3dc377..6a75e51 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,8 @@
-project(pdftohtmlEX)
+# leave this above project(pdf2htmlEX)
+# set default build type to Release
+set(CMAKE_BUILD_TYPE Release CACHE STRING "Build configuration (Debug, Release, RelWithDebInfo, MinSizeRel)")
+
+project(pdf2htmlEX)
 cmake_minimum_required(VERSION 2.6.0 FATAL_ERROR)
 
 include_directories(${CMAKE_SOURCE_DIR}/src/include)
@@ -87,18 +91,22 @@ else()
 message("Cannot locate config.h for fontforge")
 endif()
 
+# debug build flags (overwrite default cmake debug flags)
+set(CMAKE_C_FLAGS_DEBUG "-ggdb")
+set(CMAKE_CXX_FLAGS_DEBUG "-ggdb")
 
+# release build flags (overwrite default cmake release flags)
+set(CMAKE_C_FLAGS_RELEASE "-O2 -DNDEBUG")
+set(CMAKE_CXX_FLAGS_RELEASE "-O2 -DNDEBUG")
+
+# generic flags
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall")
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -O2")
-#set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -ggdb")
-
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall")
+
 # clang compiler need c++11 flag
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
 endif()
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -O2")
-#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -ggdb")
 
 # CYGWIN or GCC 4.5.x bug
 if(CYGWIN)