Two different types of the nitrogen-doped chemical vapor deposited (CVD) diamond films were synthesized with N-2 (nitrogen) and C3H6N6 (melamine) as doping sources. The samples were analyzed by scanning electron microscopy, Raman scattering, photoluminescence spectroscopy, and field-emission measurements. More effective substitutional nitrogen doping was achieved with C3H6N6 than With N-2 The diamond film doped with N-2 contained-a significant amount of nondiamond carbon phases. The sample produced with N-2 exhibited a lower field emission turn-on field than the sample produced with C3H6N6 It is believed that the presence of the graphitic phases (Or amorphous sp(2) carbon) at the grain boundaries of the diamond and/or the nanocrystallinity (or microcrystallinity) of the diamond play a significant role in lowering the turn-on field of the film produced using N-2. It is:Speculated that substitutional nitrogen, doping Plays only;a minor role in changing the field emission characteristics of CVD diamond films.