Introduction: As malignant diseases become more prevalent, and as such represent a huge public health problem and a social burden, the search for antitumor drugs is becoming more frequent. Given that cis-platinum as one of the most commonly used chemotherapeutics shows a number of side effects, and knowing the earlier antitumor properties of copper, research has been moved to investigate the antiproliferative effect of copper and copper (II) complexes. Objectives: To investigate the antiproliferative effect of new copper (II) compounds complexed with chromone-2-carboxylic acid on the growth of four cell lines (MRC-5, HT-29, HepG2 and KATO III). Materials and methods: The compounds tested during this study were: chromone-2- carboxylic acid (C10H6O4); copper (II) complexes with acetate, sulfate and nitrate synthesized at the Department of Chemistry, Josip Juraj Strossmayer University of Osijek. Compounds were previously prepared by dissolving in DMSO and the final concentration range was 10-5M, 10-6 M and 10-7M. After treatment of cell lines with compounds and incubation for 72 h in an incubator, the MTT assay determined the number of living cells. Results: Copper (II) compounds complexed with chromone-2-carboxylic acid showed an inhibitory effect on the growth of the tested cell lines. Complex Cu (II) with sulfate, or Complex II, showed the greatest cytotoxic effect, while the liver cancer cell line (Hep-G2) stood out as the most sensitive cell line. A correlation was observed between the antiproliferative effect and the applied concentration of a particular tested compound. Conclusion: Copper (II) compounds complexed with chromone-2-carboxylic acid show an antiproliferative effect on cell lines. The antiproliferative effect depends on the concentration and type of cell line.