Obesity in childhood and adolescence represents a major health problem in our century. In Greece, more than 30%-35% of children and adolescents are either overweight or obese. Using information and communication technologies, we developed a "National Registry for the Prevention and Management of Overweight and Obesity in Childhood and Adolescence" for guidance and training of Pediatricians and General Practitioners. The application supports interoperability with other national infrastructures and multi-layered security spanning preventive, detective and administrative controls. The Patient Summary Dataset includes information on medical history, family history, medications, immunizations, clinical examination and laboratory findings and appointment booking service. The application was launched in September 2015 and is accessible by: http://app.childhood-obesity.gr/. Based on the data that the doctor registers, the system calculates a personalized therapeutic algorithm that provides information on diet, physical exercise and sleep, as well as guidance on laboratory investigations and referral to specialized centres. A pilot study performed in 1270 children and adolescents indicated that using this system resulted in a reduction in obesity rates by 30% and overweight rates by 35% within 1 year. This National e-Health System appears to be effective in the management of overweight and obesity in childhood and adolescence. © 2018 Stichting European Society for Clinical Investigation Journal Foundation.