The aim of this study is to determine the purposes and characteristics of adolescents' internet use. Furthermore, the study compared adolescents' internet use purposes in terms of gender, school type and grade level variables. The study group consisted of 1002 students who were studying in 10 public high schools in 2012-2013 academic year in Istanbul. The data were collected through the Internet Use Purposes Scale (IPUS) and were analyzed using descriptive statistics, t-test and ANOVA. Research revealed that duration of internet use of adolescents' increased over years. Also, more than half of the adolescents access internet at home, in the evening and at night. Girls use mobile phone two times more than boys in order to access internet. One out of every ten adolescents were found to be at risk of internet addiction. Results indicate that adolescents use internet mostly for the communication and learning purposes whereas they use the internet for the purposes of education, psychological needs and entertainment at lower levels. Significant differences were observed in terms of gender and school types. However, grade level did not have a significant effect on the purposes of adolescents' internet use.