Ovarian cancer is a malignancy of high mortality rates. In respect of the number of deaths caused by cancers it occupies the fourth place among women in Poland. Recent studies are focusing on the role of immune system in ovarian cancer pathogenesis. It has been reported that immune response against ovarian cancer cells may be inhibited by a number of immunosuppressive mechanisms active in cancer microenvironment. It causes difficulties in recognizing and destroying cancer cells by immune system which leads to the development of immune tolerance and is associated with a low efficacy of standard therapeutic strategies. In the presented paper we have described selected, new immunosuppressive mechanisms in ovarian cancer patients. They may be a novel, additional and relevant criterion that should be considered whilst developing new therapeutic strategies. Possibly, modulation of immunosuppressive mechanisms could contribute to modifying standard therapies and in consequence improve treatment outcome in ovarian cancer patients.