Vitamin D and its active form calcitriol have multiple effects in cancer cells, such as anti-proliferative effects, induction of apoptosis and cell cycle arrest. There is a link between vitamin D metabolism and inflammatory processes, which should be considered in cancer therapy. An association between these two types of metabolism is also observed in breast and ovarian cancer. These inflammatory processes are based on an increase of cyclooxygenase-2 (COX-2) activity. The current study aimed to evaluate the expression of prostaglandin-metabolising enzymes COX-2 and 15-hydroxyprostaglandin-dehydrogenase (15-PGDH) along with the vitamin D receptor (VDR) in benign and malignant breast and ovarian tissues.VDR, COX-2, 15-PGDH and prostanoid receptor E2/E4 expression were measured in tissues by western blot analysis. Additionally, plasma 25(OH)(2)D(3) and PGE(2) levels were measured in healthy patients and cancer patients.We detected an elevated COX-2 and inversely a lowered VDR expression in cancer patients compared to healthy women. Breast cancer patients diagnosed during wintertime had a significantly lower serum level of 25(OH)(2)D(3); PGE(2) serum levels were higher in both types of cancer.These results support the idea of a link between prostaglandin and vitamin D metabolism in regards to their influences on breast and ovarian cancer.