Several radiation defects have been detected by EPR in a single-crystal of Pt(dmimt)4Cl2.4H2O (dmit = 1,3-dimethyl-imidazoline-2-thione). In order to identify these rediogenic species, the structure of the crystal has been resolved and the angular dependence of the EPR signals has been analysed. The resulting g tensors and 195Pt hyperfine tensors have been determined and the orientations of their principal axes have been compared to those of the bond directions of the precursor. It is shown that both Pt(I) and Pt(III) complexes are trapped, whereas Pd(dmimt)42+ present as an impurity, leads only to the Pd(I) species. The temperature dependende of the EPR spectra gives information about the relative stability of the paramagnetic species and shows that the formation of some species, especially the Pt(III) complexes, requires drastic modifications of the parent Pt(II) cation.