Internet addiction is characterized as a compulsive–impulsive spectrum disorder and it has four components: excessive use, withdrawal, tolerance and negative repercussions. The objective of this study is to review the world literature regarding the prevalence of Internet addiction and to verify comorbidities associated with the disorder. Pubmed, Scielo, Virtual Health Library and Google Scholar databases were consulted, and 61 articles were included in the review. The prevalence of Internet addiction is higher in developed countries and in the male gender and there are no differences among socioeconomic classes. Internet addicts have sleep disturbances, a tendency to sedentarism and overweight, low self–esteem, depression and musculoskeletal injuries.