Purpose of investigation: This study was designed to evaluate the use of human epididymis protein 4 (HE4) as a biomarker in the differential diagnosis of malignant and benign endometrial tumours. Materials and Methods: The study, conducted between July 2009 and June 2014, included a total of 150 patients with endometrioid adenocarcinoma and a control group of 150 patients with benign endometrial lesions. The serum of all patients was analyzed with respect to HE4 and CA125 levels. The median and ranges of serum levels were determined in relation to histological results. The statistical analysis procedure employed in this study utilized logarithmic-transformed values of biomarkers and logistic regression. Results: An analysis of two groups of patients with different histologies yielded a statistically significant difference (p-value < 0.05) only in the case of HE4, in which case a cut-off value of 48.5 pmol/l resulted in an achieved sensitivity of 87.8%, a specificity of 56.6%, and a negative predictive value of 81.1%. Conclusion: In combination with clinical and ultrasound findings, HE4 could help with the differentiation of prognostically varied patient groups as well as with the decision-making process associated with the development of individual treatment plans. However, the optimal cut-off for HE4 has not been established yet and further studies are needed.