New complexes of Pt(II) and Pd(II) with 2-quinolinecarboxaldehyde selenosemicarbazone were synthesized and characterized by elemental analysis, NMR and IR spectroscopy and molar conductivity measurements. The assumed geometry of Pt(II) and Pd(II) complexes was square planar where the ligand was tridentately coordinated via the quinoline and imine nitrogen atoms and the selenium atom. The cytotoxic activity of the new Pt(II) and Pd(II) compounds, as well as of some previously synthesized Cd(II), Zn(II) and Ni(II) complexes with the same or analogous ligand, was tested against a panel of three human cancer cell lines: human cervix carcinoma cells (HeLa), human melanoma cells (FemX) and breast cancer cells (MDA-361). All investigated compounds, except Pt(II) complex, possess a strong dose-dependent cytotoxic activity of the same order of magnitude as cisplatin (CDDP). The investigation of potential of these compounds to induce HeLa cell cycle perturbations was also evaluated.