This paper deals with an investigation of the trapping mechanisms and the “pumping” process on a device based on polycrystalline Chemical Vapor Deposited (CVD) diamond, recently tested as particle tracker. Photoconductivity measurements have been carried out during monochromatic illumination from near IR to above bandgap, while thermally stimulated current measurements have been used to detect a main defect level near band‐edge. The results have been compared with charge collection distance measurements, highlighting the passivation effects of some trap levels due to irradiation. Based on these data we suggest a band‐gap and trap‐state model for CVD diamond presently used in particle physics experiments. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)