The prevalence of childhood obesity increases dramatically. First signs of cardiovascular diseases and type 2 diabetes appear early in life. The treatment of childhood obesity aims at weight maintenance during growth, normalization of body mass index at long-term and prevention of complications. The family based behavioural therapy is a promising approach. It provides simultaneous treatment for the overweight parent and child in order to modify the family environment, to provide role models and support for child behaviour changes. However, this requires group leaders and multiple counselors to meet with families. The treatment should be initiated as soon as possible, as its efficacy is reduced after the onset of puberty. Early preventive interventions that aim to modify both individual's behaviours and the environment are needed.