Natural diamond is considered an optimum electronic material due to the uniqueness of its properties (i.e. Johnson figure of merit, breakdown voltage, maximum allowable frequency, thermal conductivity, etc.). However, due to the limitation of geological diamond, electronic devices based on this material have found only restricted usage. On the contrary, polycrystalline diamond deposited by CVD techniques is considered a new "wide bandgap material" which can be tailored to fulfill the requirements of the industry for the development of electronic devices. Therefore, temporal response of thin film polycrystalline materials often differ significantly from those of single crystalline bulk materials because of grain boundary effects. We have used a modulated 8.06 keV X-ray beam to study the photoconductive response of films deposited by a CVD technique. The collection efficiency of charge carriers under irradiation both in DC and AC conditions has been studied to infer the transport mechanisms as a function of the modulation frequency and film morphology. The evolution of the device sensitivity to the ionising radiation has been analysed and a correlation with the mobility-lifetime product is proposed. Finally, achieved results will be correlated with sub bandgap photoconductivity spectra able to evaluate the amount of grain boundary related defects.