Objectives: Recent evidence suggests that epithelial ovarian cancer (EOC) does not derive from ovarian surface epithelium but from the tissues of Mullerian origin, particularly from the fallopian tube. HE4, a protein of Mullerian origin, seems to be promising marker for EOC detection and treatment monitoring. This study was designed to compare the expression of WFDC2 gene, encoding HE4 protein, in normal tissue of the ovary, fallopian tube and EOC. The correlation between WFDC2 expression in cancer tissue and serum level of HE4 was additionally measured. Material and methods: Tumor specimens were obtained from EOC patients during primary surgery before chemotherapy. Samples of normal ovaries and fallopian tubes were collected from healthy patients operated for other reasons. Total RNA was isolated from the tissues and relative WFDC2 expression was evaluated by Real Time RTqPCR. HE4 serum level in cancer patients was measured using COBAS System. Results: EOC samples were distinguished by much higher WFDC2 expression in comparison to normal ovaries (p=0.000016). Transcriptional activity of WFDC2 in EOC specimens and in normal fallopian tubes was comparable (p=1.00). Additionally, lack of correlation between WFDC2 expression in cancer tissue and serum level of HE4 protein in ovarian cancer patients was observed (p=0.3). Conclusions: High expression of WFDC2 was demonstrated for both, EOC and fallopian tube, as opposed to its low expression observed in normal ovaries suggesting that EOC is derived from fallopian tube rather than ovary. Elevated HE4 serum concentration in EOC patients is not correlated with higher gene expression in cancer tissue.