Computer games are the most popular enter tainments in modern societies and they target a variety of people in different ages. The addiction to the rivalry and excitements of the games make them the most common recreational programs for today's teenagers, so that they do anything to reach a higher level of the game, they immerse in the game so much that they completely separate from their surroundings. Challenging with the obstacles and reaching a higher level in the game, make the players excited and losing the game make them anxious.1 Computer games started in 1972 with Pang, a computer tennis game, and then developed in hardware and software systems. Improvement of quality and variety of games increasingly spread it in the society especially adolescences.2 It is believed that computer games like watching TV provides opportunities for visual learning. Especially because these games are more active compared to watching TV, they are considered more effective.3 Since these games are known as the second entertainment after TV, opponents of these games emphasize on their negative effects such as stimulating anger and violence, costing a lot of money and having negative effects of physical and mental health, which are much higher than the positive effects of the games such as increasing the coordination of eyes and hands.4 As Klein and Keepers mentioned in their research reports in 1990, students who prefer computer games to other entertainments have more behavioral problems that other students (cited from Patton).5 Currently in Iran, a great part of students' lei sure time out of school is spent on computer games.6 The reasons for adolescents' attraction to these games include being excited and easily accessible while authorities and families do not have any proper plan for students' leisure time and there is not many options for their enter tainments. Playing computer games to some ex tent can be useful, but longterm playing leads to various physical and mental complications.7 Long term involvement with these games means the players long term tension, restlessness and worrisome and during the game, physical ten sions and real physical stimulations are experi ences. By sympathetic nervous system stimula tion, this can gradually make this system sensi tive and ready for response to limited stimu lants, while causes anxiety symptoms in the player. A study by Sherry et al (2001) investigat ing the reasons for playing video and computer games by adolescents and their game priorities on 535 adolescents in age 1520 in the West USA found that 68% of adolescents had these games as their weekly entertainment. The reasons for playing these games among boys were excite ments and challenges and they insisted to win. Moreover, sport and violent games were more attractive for boys.8 Development of electronic and computer games are a great threat for youth and adoles cents and can lead to psychological disorders and depression in these groups. In previous times, kids were involved playing with other children, but children of today spend most of their time on computer games as soon as they understand and acquainted with them, while these games cannot create any emotional and human relationship.9 Children's and adolescents attractions to the computer games cause many mental, physical and social problems for them. These effects are stimulating anger and violence, obesity, epilepsy due to games, social isolation, and other physical and mental damages. Many psychologists and mental health professionals have paid attention to the effects of these games.10 The increasing prevalence of computer games among children and adolescents have made many researchers to determine the effects of these games on players. In Iran, there are few and limited studies on the effects of addiction to computer games on players. Considering the increasing rate of addiction to computer games among Iranian adolescents and youth, the pre sent study was conducted to investigate the ef fects of addiction to computer games on physical and mental health including physical health, anxiety, and depression and impaired social functioning.