A review of the literature and the authors' recent researches on the treatment of internet addiction among adolescents based on a cognitive behavioral approach suggest that most severely addicted adolescents have various co-morbid psychiatric problems and that the cognitive behavioral approach in a group setting is effective in the improvement of not only addictive behavior but also emotional and general behavioral problems including insight, depression, anxiety, and impulsiveness. Adolescents with internet addiction, especially who are severely affected, need a comprehensive psychiatric treatment of co-morbid problems and other behavioral problems.