Current state-of-the-art behavioural treatments for childhood and adolescent obesity, produce long-term weight control in up to one-third of participants. A review of the most effective treatments suggests structural and organizational components and treatment content that are most likely to be successful. These include a group format with individualized behavioural counseling; parent participation; frequent sessions; a long treatment duration; a simple and explicit diet that produces a calorie deficit; a physical activity program emphasizing choice and reinforcing reduced sedentary behaviours; making changes in the home and family environment to help reduce cues and opportunities associated with calorie intake and inactivity, and to increase cues and opportunities for physical activity; self-monitoring; goal setting and contracting; parenting skills training; skills for managing high-risk situations; and skills for maintenance and relapse prevention. Still, there are many unanswered questions about the implementation of all the components of treatment. Further research, to identify treatment approaches that promote long-term maintenance of weight control, is greatly needed.