This article provides current guidelines on the treatment and prevention of childhood obesity. Since factors involved in obesity change with age, the therapeutic approach in pre-school children will be different from pupils and adolescents. The treatment will also be modulated on the basis of weight excess, weight gain velocity and complications. The main goal of the treatment should be to encourage the child and his family to have healthy lifestyle. Families who are not ready for change might benefit from counselling to improve motivation before starting treatment. A detailed alimentary and behavioural history is the start point of the treatment. The strategy of the intervention is to induce changes at three levels: 1) attitudes of parents; 2) physical activity; 3) energy intake. The treatment of the adolescents should take into account the pubertal changes and the psychological aspects of this peculiar period of life. Obesity is a chronic disease and its treatment needs long-life follow-up. The long-term results of the obesity treatment are often disappointing and we have to consider consistent prevention programs for better results.