Discontinuous and continuous diamond films with different morphologies and qualities were deposited on n(2+)-type Si(100) substrates, using the hot-filament chemical vapor deposition (CVD) technique from CH4-H-2 gas mixtures. The field-emission characteristics of these diamond films were investigated. The rum-on fields at a 0.01mA/cm(2) current density were recorded for all the tested CVD-diamond films. It was found that discontinuous diamond films showed a much lower turn-on field (1.2 V/mu m) than continuous ones (20 V/mu m). The effective working function of continuous diamond films was around 0.1 eV, while that for discontinuous diamond films is about 0.03 eV. O-2 plasma post-deposition sharpening of thick diamond films indicated that the geometrical-field enhancement, caused by the surface topographic changes, has no significant influence on the turn-on field.