Two new Pt(II) complexes [PtCl(C2H4)(MeQO)] (Q1) and [PtCl(C2H4)(NO2QO)] (Q2) were synthesized by the interaction of Zeise’s salt with either MeQOH or NO2QOH, respectively. Structures of Q1 and Q2 were determined by ESI MS, IR, 1H NMR spectroscopies. The results indicated that deprotonated MeQOH and NO2QOH (MeQO/NO2QO) coordinate with the Pt(II) via both the N and O atoms. The ethylene bonds with Pt(II) in the η2 manner and in trans position with respect to the N atom. The result of in vitro cytotoxicity test indicated that complexes Q1 and Q2 exhibit excellent activities against KB, Hep-G2, Lu, MCF-7 cell lines with IC50 values of 0,4-1,2 µM, much more active than cisplatin (IC50 = 13,3 – 45,7 µM). Remarkably, these two complexes display cytotoxicity against MCF-7 and KB 37-57 times higher than cisplatin. Furthermore, Q1 shows 4 times lower toxicity on nomal cell (HEK-239) than the four cancer cells.