OBJECTIVE The present paper aims to investigate the effects of both progesterone and progestin treatment mainly related to the occurrence of breast cancer in women. METHODS Extensive systematic bibliographic review of Greek and International articles was conducted through the electronic databases Pubmed, Cinahl, Uptodate, and Google Scholar for the identification of articles related to progesterone, progestins and breast cancer treatment. RESULTS Hormone therapy with the use of estrogen alone presents a small increased risk or does not present at all an increased risk of breast cancer. With ORs in some studies below 1.0 in current users for 3 plus years and safe option until 7 years, while in other studies the risk was increased with the ORs 1.29. However, the use of estrogen in combination with progestogens, depending on the type of progestogens, shows an increased risk of breast cancer, with the ORs to vary between 1.14- 2.38 from 3 to 5 years and is inversely proportional to the time of its use. This risk varies depending on the combination of the preparations. Other factors that are associated with breast cancer risk when receiving hormone therapy are the years that hormone therapy is taken, directly proportional to the risk. At higher risk are older women, women with low body mass index in menopause (BMI <25kg/m2) and women with increased mammographic breast density. Continued use of hormone therapy is associated with an increased risk for breast cancer compared to sequential. The risk became visible sooner to women who used in the past hormone therapy and were using it again. Starting hormone therapy in the immediate postmenopausal period also increased the risk for breast cancer. Hormone therapy was associated with tumors with positive estrogen and progesterone receptors, and also the lobular histological type was associated with its use. Tibolone use was associated with an increased risk.