The structures of cis-diamminechloro(guanosine-N-7)platinum(II) nitrate dihydrate, cis-[PtCl(NH3)(2)(C10H13N5O5)]NO3 .2H(2)O, (I), and chloro(ethylenediamine)(1-methylimidazole-N-3)platinum(II) nitrate, [Pt(C2H8N2)(C4H6N2)Cl]NO3 , [PtCl(en)(1-MeIm)]NO3, (II), were determined by single-crystal X-ray diffraction. The former complex crystallized in the orthorhom bic system and the latter in the monoclinic system. In compound (I), water molecules were found to connect the metal complex with the nitrate counter ions via hydrogen bonding.