A systematic investigation of deposition parameters and post-treatments was performed for the development of field emission displays based on flat chemical vapor deposited diamond films. The lowest onset field strengths were obtained for films grown at the highest substrate temperature, highest methane content, and with negatively biased substrate. Intentionally damaging the films by implantation with 50 keV and 100 keV carbon ions as well as with 4.4 MeV silicon ions usually resulted in an enhanced field emission. The emission followed the Fowler-Nordheim law up to 0.5 mA/mm(2), and a current carrying ability of more than 100 mA/mm(2) was detected. Considerably improved emission was achieved by short and long-term processing at higher current levels.