Research objectives: The aim of this paper was to demonstrate immunohistochemical staining important for diagnosis and differential diagnosis of epithelial ovarian tumors, to investigate the number of diagnosed epithelial tumors and to classify them according to the type and malignant potential, and to evaluate the intensity of expression of immunohistochemical markers in relation to the intensity of expression of positive tests in relation to the type of epithelial tumor. Materials and methods: The material consists of samples of ovarian tumor stored in a two-year period in the Archives of the Department of Pathology and Forensic Medicine of the University Hospital Osijek. They were processed by histochemical procedure and stained with hematoxilin and eosine (HE), and processed by an indirect ABC method with antibodies for CK7, CK20, WT1, Ca125 and CDX2. The expression of immunohistochemical markers in relation to the positive test has been described by light microscope. Results: In a two-year period a total of 102 epithelial ovarian tumors were diagnosed, out of which 59.80% were serous, 34.31% mucinous, 2.94% clarocellular, 0.98% Brenner tumors, and 1.96% metastatic ovarian tumors. Out of 102 tumors, only 10 of them were treated by immunohistochemical methods, ie 9.80%. Tumor marker CA125 had on most preparations weaker intensity of the positive tests, whereas in contrast, CK7 had on most preparations higher intensity, and the marker CK20 had on most preparations the color intensity equal to the intensity of the positive probe. Conclusion: At the Department of Pathology and Forensic Medicine of the University Hospital Osijek the most commonly diagnosed were serous ovarian tumors of benign nature. Immunohistochemical methods were performed on 10 tumors, meaning that in the diagnosis of ovarian tumors immunohistochemistry is not as widely used as histological methods. Different tumor markers showed different expression in relation to the positive test.