OBJECTIVE: To review data about the nutrition of physically active children and adolescents. METHOD: Review of literature using MEDLINE and LILACS data base and the keywords sport or physical activity and nutrition and children or adolescents. RESULTS AND CONCLUSION: Involvement of children and adolescents in sports activities is important for their growth and development process, which should be regularly assessed. Na adequate diet should provide enough energy and nutrients so that young athletes can meet their requirements. The diet should suit the different stages of training, before, during and after competition. Hydration should be planned carefully as children present a less efficient thermoregulation than adults and can dehydrate more quickly, specially during sports practice. Female athletes can present menstrual alterations and inadequate bone growth due to excessive training associated with inadequate energy intake. Eating disorders are found among some groups of athletes. Physical activity should be encouraged as part of the treatment of overweight children.