The authors investigated field emission characteristics of nitrogen-doped diamond films, which were grown using microwave plasma-enhanced chemical vapor deposition. Nitrogen-doped films showed low turn-on voltages below 2 V/mu m. Secondary ion mass spectroscopy was used to compare nitrogen concentrations in the films. Morphologies, Raman spectra, the resistivities, and surface roughness of the films were changed as the nitrogen concentrations varied. The field emission properties of heavily nitrogen doped diamond films were related to the film resistivity, surface morphologies and Raman characteristics.