[en] Platinum(2) cis-diamminocomplexes isomerize under γ-irradiation. Isomerization of cis-diiodocomplexes of platinum(2) occurs easier and at the lower doses with respect to decomposition with metal deposition. Isomerization of cis-diiododiamminoplatinum(2) polycrystals proceeds under γ-irradiation with respect to analogous reaction with cis-dichlorodiamminoplatinum(2). This may be explained by the higher trans-influence of the iodogroup with respect to that of chlorine. Investigation was performed using UV and IR spectra in the region of absorbed dose from 100 to 2000 Mrad