It's undoubted that optimum nutrition for term infants is breastfeeding, exclusive for the first six months, then followed by a complementary diet and carried on, if possible, for the first year of life or even more. During the last decades several data confirmed the great advantages of fresh mother's milk use also for feeding very low and extremely low birthweight preterm infants. When mother's milk is unavailable or in short supply, pasteurized donor breast milk is widely used in neonatal intensive care units. Pasteurization partially affects nutritional and immunological properties of breast milk, however it is known that pasteurized milk maintains some biological properties and clinical benefits. The substantial benefits of mother's own milk feeding of preterm infants are supported by strong evidence. However, there is increasing evidence also on specific benefits of donor breast milk. Future research is needed to compare formula vs. nutrient fortified donor breast milk, to compare formula and DM as supplements to maternal milk rather than as sole diet and to compare effects of different methods of heat treatments on donor human milk quality.