The role of breastfeeding as protective factor for breast cancer incidence is controversial among scientific literature. The Interdisciplinary Senology Unit of Trieste has analyzed the relation between breast cancer incidence and lactation habits among a total of 4307 Trieste’s women. In this study, the statistical analysis revealed that over having children, the breastfeeding is a further protective factor for breast cancer. In particular, the decrease of breast cancer risk by breastfeeding resulted to be significant for lactation more than 12 months. It is worth noting that breastfeeding resulted protective only for women in childbearing age and it didn’t result to decrease breast cancer risk among post-menopausal women.