The concept of Internet addiction, also called Internet addictive disorder or pathological Internet use, entered the medical lexicon in 1995. To investigate the prevalence of Internet addiction among north Iranian Internet users and to explore the epidemiological features associated with Internet addiction, for the first time in Iran, this study performed.

A total of 1856 Internet user volunteers' from Mazandaran province cities were surveyed using Farsi version of Young's Internet Addiction Questionnaire during 2005_2006. Data analysis was done using the SPSS 13.0 Win Program for descriptive and correlational statistics.

Total of 424 Dependents was in our sample. The incidence rate of Internet addiction was 22.8%. Dependents spent an M = 14.42, SD = 13.74 hours per week compared to Non-Dependents who spent M= 9, SD = 10.37 hours per week (P<0.001). The sample of Dependents included 256 males and 165 females (P<0.001). Mean±SD of Income Used for On-line Service Fees was 30.11±25.27 percent in Dependent group and 18.90±20.79 in Non-Dependent group (P<0.001). Dependents predominantly used the two-way communication functions available on the Internet like chat rooms (P<0.001).

The present study suggests that Internet addiction is frequent among northern Iranian Internet users. In addition, chat rooms are most addictive web environment in this population. The results have important implications for further studies of prevalence, implementation of preventive measures, and the development of treatment approaches for Internet addiction.