The present work describes the synthesis, solvolysis and cytotoxic activity of Pt (II) complexes of the type trans-[PtCl2 (DMSO) (L)] and cis-[PtCl2(L)2], where L = benzhydrazide (BH), 4-nitrobenzhydrazide (4NH) and 4-(trifluoromethyl)benzhydrazide (4 TF). The structures of these complexes were proposed using spectroscopic methods. All complexes undergo fast solvolysis generating four identical species in DMSO, being that the species cis- and trans-[PtCl2 (DMSO) (L)] are the most important. As to the stability in DMF, Pt (II) complexes of the type cis-[PtCl2(L)2] are very stable, while Pt (II) complexes of the type trans-[PtCl2 (DMSO) (L)] react at a slower rate than those verified in DMSO. The cytotoxic activity of the compounds was evaluated in a chronic myelogenous leukemia cell line. A relationship between solvolysis and cytotoxic activity was verified. Moreover, our results showed that some Pt (II) complexes were more cytotoxic than the free ligands, carboplatin and cisplatin.