Background: Comparison of predictive values of complete blood count inflammatory parameters and serum CA-125 levels in the differential diagnosis of patients with epithelial ovarian tumor (EOTs) diagnosed in the reproductive period. Materials: In this study, 105 women patients in the reproductive period were retrospectively analyzed. The patients included were examined in terms of clinical, laboratory and pathological features. Results: The mean age of the patients was 41.5 ± 8.6 years and BMI was 28.6 ± 5.8 kg/m2. Of the whole study population, 54 (51.5%) were benign EOTs, 18 (17.1%) were borderline EOTs and 33 (31.4%) were malignant EOTs. When comparing these three tumor groups, a significant difference was found in terms of serum CA-125 [14.7 U/mL (2.7-238.6) vs 60.2 U/mL (7.8 – 557) vs 416.5 U/mL (2.4-7695), p<0.001, respectively], platelet count [294 x103/ μL (133-744) vs 303, x103/ μL (160-468) vs 383 x103/ μL (128-725), p = 0.018, respectively], neutrophil count [4.2, x103/ μL (1.9 -8.9) vs 4.9 x103/ μL (2.6- 10.9) vs 5.1 x103/ μL (2.2 – 10.7), p = 0.012], neutrophil-to-lymphocyte ratio (NLR) [2.1 (0.1-8.2) vs 2.6 (1.2 – 5.9) vs 3.1 (1-6.8), p = 0.021, respectively] and platelet-to-lymphocyte ratio (PLR) [154.4 (82.1-658.4) vs 168.1 (91.1-377.8) vs 201.5 (29.6-499.2), p = 0.008, respectively] values. In the ROC analyses, serum CA-125 levels (AUC= 0.818, p <0.001), platelet count (AUC= 0.673, p = 0.005) and PLR (AUC= 0.690, p = 0.002) values significantly predicted malignant EOTs. Conclusion: Preoperative platelet count, neutrophil count and PLR predict epithelial ovarian cancers significantly. However, diagnostic predictive values of all three parameters are lower than CA-125. Therefore, CA-125 is still the most valuable serum biochemical marker that can be used in the preoperative differential diagnosis of EOTs.