Cow´s milk represents a very important source of proteins of high biological value and calcium in the child´s diet. The aim of this article is to review the available evidences of its role in nutrition of young children and school age children. Its main benefits are related with effects in linear growth, bone health and oral health, as protein source in early severe malnutrition, and it does not appears to influence metabolic syndrome risk and autism. High protein content in cow´s milk and increased protein consumption by children during the complementary feeding period is associated to the risk of developing a high body mass index and obesity in school-age children; therefore, milk consumption should be mildly restricted during the second year of life and to 480-720 ml/day during the first years of life. Its relationship with some diseases has not been confirmed, and milk consumption is associated with iron deficiency. The use of low-fat cow's milk instead of regular milk in young children remains controversial and its introduction is not advised before 2 to 4 years of age.