The platinum(II) mixed ligand complexes [PtCl(L1-6)-(dmso)] with six differently substituted thiourea derivatives HL, R2NC(S) NHC(O)R′ (R = Et, R′ = p-O2N-Ph: HL1; R = Ph, R′ = p-O2N-Ph: HL2; R = R′ = Ph: HL 3; R = Et, R′ = o-Cl-Ph: HL4; R2N = EtOC(O)N(CH2CH2)2N, R′ = Ph: HL 5) and Et2NC(S)N= CNH-1-Naph (HL6), as well as the bis(benzoylthioureato-κO,κS)-platinum(II) complexes [Pt(L 1,2)2] have been synthesized and characterized by elemental analysis, IR, FAB(+)-MS, 1H-NMR, 13C-NMR, as well as X-ray structure analysis ([PtCl(L1)(dmso)] and [PtCl(L 3,4)(dmso)]) and ESCA ([PtCl(L1,2)(dmso)] and [Pt(L 1,2)2]). The mixed ligand complexes [PtCl(L)(dmso)] have a nearly square-planar coordination at the platinum atoms. After deprotonation, the thiourea derivatives coordinate bidentately via O and S, DMSO bonds monodentately to the Pt11 atom via S atom in a cis arrangement with respect to the thiocarbonyl sulphur atom. The Pt-S-bonds to the DMSO are significant shorter than those to the thiocarbonyl-S atom. In comparison with the unsubstituted case, electron withdrawing substituents at the phenyl group of the benzoyl moiety of the thioureate (p-NO2, o-Cl) cause a significant elongation of the Pt-S(dmso)-bond trans arranged to the benzoyl-O-Pt-bond. The ESCA data confirm the found coordination and bonding conditions. The Pt 4f7/2 electron binding energies of the complexes [PtCl(L1,2)(dmso)] are higher than those of the bis(benzoylthioureato)-complexes [Pt(L1,2)2]. This may indicate a withdrawal of electron density from platinum(II) caused by the DMSO ligands.