Metformin, a drug from the biguanide class, is now one of the most widely used drugs in the treatment of type 2 diabetes. This drug was also used in the treatment of polycystic ovarian syndrome and recent reports indicate the possibility of using this drug in oncology. Latest findings show that metformin has an anticancer effect. Influencing the transduction mechanisms primarily through activation of protein kinase activated by 5'AMP (AMPK) regulates the activity of the AMPK/mTOR signaling pathway. MTOR pathway dysregulation may be a factor in the pathogenesis of various human diseases, especially cancers. Overactivation of mTOR is observed in malignant cells and is associated with their resistance to treatment. It can therefore be concluded that metformin as an inhibitor of mTOR may be a factor that suppresses tumor development. There are also studies showing that metformin prevents the formation of metastases, reducing tumor vasculature and improves the effectiveness of anticancer drugs. The anticancer effect of metformin has been proven in the treatment of colorectal and breast cancer. The current studies reports the positive effects in the treatment of gynecological cancers such as ovarian, endometrial and cervical cancer. Incidence for these tumors in 2009 in Poland was: for ovarian cancer 11.01100000; for endometrial cancer 15.0/100000; for cervical cancer 10.5/100000. Metformin has antitumor activity in monotherapy and also synergistically with other anticancer agents. Metformin has antiproliferative properties; reduces the VEGF levels, causing a reduction in tumor vasculature; causes an increase in progesterone receptor, which increases the response to hormonal therapy; inhibits the expression of glyoxalase I, mediating resistance to chemotherapy; decreases in the concentration of human telomerase; reduces the activity of Akt and Erk kinases, key regulators of metabolism and progression of tumors and also inhibits the formation of metastases.