Due to the radiation damage resistance and to the tissue-equivalent properties, diamond is considered one of the most suitable active material for the realization of x-ray detectors, especially for medical applications. The development of enhanced CVD techniques made possible an effective tailoring of the material properties in an effort to meet the requirements of specific applications where the substitution of the rare and costly natural diamond was solicited. CVD diamond shows a polycrystalline structure in which the material quality largely influences the photoconductive response of the resulting detectors. The control of the material properties during the growth process and the optimal design of the final detector represent the main aspects we considered. We realized x-ray dosimeters with different diamond film morphology and tested them in DC and AC conditions by a beam generated by a standard Copper tube (CuKα at 8.05 keV). The analysis of the μτ product, affecting the detector collection efficiency, and of the density of shallow states in the band-gap in proximity of the valence band, affecting the response time and intensity, were correlated with important parameters as the crystal grain quality and the grain boundary contamination. Moreover, a study regarding the influence of an irradiation bias on the detector response and an operative definition of the priming process were performed.