Understanding the role of immunological memory mediated by T-lymphocytes in patients with malignant tumors is a pressing issue. This study aimed to assess the contribution of memory T-cells to antitumor immunity in patients with ovarian cancer undergoing neoadjuvant chemoimmunotherapy with recombinant interferon-gamma (rIFNγ). Quantification of central (Tсm) and effector (Tеm) memory T-cells (Тm), as well as naive T-lymphocytes (Th0), was done using flow cytometry. Compared to healthy females, untreated cancer patients were found to have more Tm and less Th0 cells in their blood CD4⁺ and CD8⁺ T-cell subpopulations. In cancer patients, Tm cells accumulated in the ascitic fluid, exceeding 7.7 times the number of CD4⁺ Th0 cells and 6.5 times the number of CD8⁺ Th0 cells, with Tem prevailing over Tcm. After chemotherapy with rIFNγ, blood Th0 decreased in cancer patients, while Tcm dominated the CD8+ Tm subpopulation both in the blood and ascitic fluid. Tem cells were a prevalent cell type in patients who received chemotherapy without interferon-gamma. Decreased Th0 and Tcm prevalence were a positive sign accompanied by a good response to treatment, including lower relapse rates (46.7 % vs. 80 % in controls) and a longer relapse-free period (17.5 ± 1.6 vs. 11.3 ± 1.5 months in controls). Therefore, we conclude that chemoimmunotherapy alters proportions of T-cell subpopulations in the blood and ascitic fluid of patients with ovarian cancer, with Tcm cells prevailing over Tem, which may be one of the mechanisms of rIFNγ (Ingaron) action.