Polycystic ovarian syndrome (PCOS) is the most common endocrinopathy among women of reproductive age. In addition of fertility problems, there are numerous potential mechanisms which could promote neoplastic disease, including breast and gynecological cancers (endometrial and ovarian cancers), in women with PCOS. PCOS patients have a higher prevalence of obesity and consequently higher risk of metabolic syndrome. Also, hyper and rogenism, as one of the main symptoms of PCOS, is the result of endocrine alterations like increased presence of androgens and estrogens secreted abnormally. Obesity and fertility disorders caused by PCOS are two important risk factors for various cancers such as ovarian cancer. There is some evidence, which suggests that PCOS may be assumed as a factor in the increased risk of ovarian cancer. Also, androgen levels, weight gain and obesity are the main risk factors for the onset and progression of breast cancer. Related articles in English were searched in PubMed, Google Scholar, Elsevier, Wiley Online Library. Accordingly, PCOS could be known as a cause of estrogen-dependent tumors that have receptors for steroid hormones, such asbreast and ovarian cancer. Despite the on going extensive research aiming to determine the relationship between PCOS and increased risk of developing breast and ovarian cancers, limited information has been obtained to confirm this relationship.