We have demonstrated the applicability of DLTS to semiconducting diamond thin films. This paper includes details on the capacitance-voltage measurements, the DLTS spectrum and the DLTS spectra as a function of bias. Our study was done with an aluminum Schottky contact on polycrystalline diamond film. We found a strong temperature dependence of the Schottky diode capacitance with a reduction of effective dopant concentration from 4 × 1014 cm−3 at 300K to 2 × 1014 cm−3 at 200K. The DLTS signal had a good signal to noise ratio, characteristic line-shape and clear peaks. The trap concentration was 8 × 1013 cm−3 (at 400/s rate window) with an activation energy of 0.31 eV and a capture cross section of 1.15 × 10−18 cm−2. The spectra showed a bias dependence of peak height and position.