Electroporation (EP) is a physical technique in which an electric field is applied to cells in order to increase the permeability of cell membrane for poorly permeating molecules. Electroporation in combination with cisplatin (CDDP), also called electrochemotherapy (ECT), is used for local treatment of several malignant tumors. Cisplatin is a well-known platinum (II) antitumor drug which antitumor activity has been linked to its ability to form DNA adducts, which subsequently lead to apoptosis of cancer cells. Although CDDP is broadly used, its main limitations are severe side effects and tumor cells’ resistance. Because of this, researchers are focusing on developing new platinum (II) complexes with antitumor activity, including [PtCl (5,7-dibromo-8-hydroxyquinolinato)(S-dmso)] (compound A) and it's analog, [PtCl (5,7-dibromo-8-hydroxyquinolinato)(pta)] (compound B). In the thesis, we analysed the cytotoxicity of compound A and B in combination with EP in human colon cancer (HT29) and human breast cancer cell line (MCF7). We determined IC50 values with clonogenic assay and compared it to IC50 values of CDDP. We used Giemsa staining to determine the percentage of apoptotic and necrotic cells. Results show that all compounds, A, B and CDDP have a cytotoxic effect on both tumor cell lines and cause primarily apoptotic cell death. Furthermore, EP has proved to be a very effective method for drug uptake as it has significantly improved cytotoxicity of all three platinum (II) complexes. Compound B has turned out to be more cytotoxic with and without EP than compound A and showed similar or better cytotoxicity than CDDP in both cell lines. Based on our results, compound B is very promising potential therapeutic agent.