The detection properties of heteropitaxial (polycrystalline, pCVD) and homoepitaxial (single crystal, scCVD) diamond films grown by microwave chemical vapor deposition (CVD) in the Laboratories of Roma ''Tor Vergata'' University are reported. The pCVD diamond detectors were tested with a-particles from different sources and 12 C ions produced by 15 MV Tandem accelerator at Southern National Laboratories (LNS) in Catania (Italy). pCVDs were also used to monitor 14 MeV neutrons produced by the D-T plasma at Joint European Torus (JET), Culham, U.K. The limit of pCVDs is the poor energy resolution. To overcome this problem, we developed scCVD diamonds using the same reactor parameters that optimized pCVD diamonds. scCVD were grown on a low cost (1 0 0) HPHT single crystal substrate. A detector 110 mm thick was tested under a-particles and under 14 MeV neutron irradiation. The charge collection efficiency spectrum measured under irradiation with a triple a-particle source shows three clearly resolved peaks, with an energy resolution of about 1:1%. The measured spectra under neutron irradiation show a well separated 12 Cðn; a 0 Þ 9 Be reaction peak with an energy spread of 0.5 MeV for 14.8 MeV neutrons and 0.3 MeV for 14.1 MeV neutrons, which are fully compatible with the energy spread of the incident neutron beams.