The present study was carried out to assess the percentage of T helper 17 (Th17) lymphocytes in blood and tissue and IL-17A serum concentrations in patients with epithelial ovarian tumors. Two isoforms, IL-17A and IL-17F, as well as IL-21 and IL-22, were simultaneously investigated. The study group consisted of 60 women affected by epithelial ovarian tumors (benign, borderline and malignant) and 20 women without ovarian pathology as a control group. The evaluation of the percentage of Th17 cells secreting IL-17A, IL-17F, IL-21 and IL-22 in peripheral blood and tumor tissues was performed using flow cytometry applying a Th17 cytokine staining panel. The blood serum concentration of IL-17A was determined using ELISA. We found no statistically significant differences in the subpopulations of Th17 lymphocytes, either in peripheral blood or in ovarian tissues, following comparison of the women with and without ovarian pathology. Negative correlations were found between the percentage of CD4+/IL-21+ (rs=0.8, p=0.02) and CD4+/IL-17+ (rs=-0.78, p=0.03) in the tissue and IL-17A in blood serum in the group of patients with borderline ovarian tumors. A negative correlation was also found between IL-17A and the percentage of CD4+/IL-21+ in peripheral blood (rs=‑0.48, p=0.03) in the group of patients with ovarian cancer. The increased percentage of Th17 cells in tissue was not correlated with the overall survival of the ovarian cancer patients. In conclusion, we showed that more Th17 cells secreted IL-17A and IL-21 in the tissue of borderline ovarian tumors and less IL-17A in serum. We also observed that in peripheral blood of the patients with ovarian cancer, there was a higher percentage of Th17 lymphocytes and a lower concentration of IL-17A in serum indicating a negative correlation. An increased percentage of Th17 cells in ovarian tissue does not influence the time of survival of patients with ovarian cancer.