Overweight children are at an increased risk of becoming obese adults, which may lead to shorter life expectancies in the current generation of children as compared to their parents. Furthermore, being an overweight child has a negative psycho-social impact. We consider obesity in children and adolescents a chronic illness, which is in line with the American Medical Society. We summarize the evidence for the efficacy of a combination of diet, physical activity and behavior-focused interventions in a family-based setting. The present guidelines propose a multidisciplinary service implemented as a "chronic care model" based on "best clinical practice" inspired by an American expert committee and the daily practice of The Children's Obesity Clinic at Copenhagen University Hospital Holbaek. Children and adolescents should be referred for examination and treatment in a pediatric setting when BMI corresponds to an isoBMI of minimum 30 or BMI corresponds to an isoBMI of 25 and complex obesity is suspected. Obtaining a thorough medical history is pivotal. We propose a structured interview to ensure collection of all relevant information. We recommend physical examination focused on BMI, waist circumference, growth, pubertal stage, blood pressure, neurology and skin and provide comprehensive paraclinical investigations for obesity and obesity related conditions. Treatment of obesity in children and adolescents is fully dependent on the combined effort of the entire family. This cannot be overemphasized! The main principle of the treatment is developing an individual detailed plan for every patient to reduce caloric intake whilst increasing physical activity, leaving no ambiguity with the recommendations.