Introduction. Due to the rapid development of nanotechnology, selenium nanoparticles (NPs) have recently attracted much attention due to their unique physical and chemical properties for biomedical applications, in particular for the treatment of oncological diseases. The review considers the selenium nanoparticles, which are widely studied in the field of oncology.Text. This review is devoted to the analysis of scientific literature on the anticancer activity of selenium nanoparticles against human cancer cell lines, as well as the application of these nanoparticles as a drug delivery system. Besides, the antitumor mechanisms of selenium nanoparticles against malignant neoplasms are discussed.Conclusion. According to the results of literary data analysis, it was found that selenium nanoparticles exhibit a good antitumor effect against various human cancer cell lines. It is shown that the antitumor activity of selenium nanoparticles is mainly related to activation of the extrinsic and intrinsic signaling pathways of apoptosis leading to cancer cell death. Also, selenium nanoparticles are promising systems for delivery of various anticancer drugs, providing high efficiency, bioavailability of drugs in tumor cells and minimizing toxicity to healthy cells.