This study was conducted to determine the general characteristics of Internet use among high school students in Turkey and to examine the relation between the Internet use and the academic performance of the students. The population of the research consisted of 1100 randomly chosen high school students, studying at 4 state high schools during the academic year of 2008-2009 and the sample of the study included 804 high school students willing to participate in the research and studying at these schools during the same period. Data were collected by the investigators using the survey form prepared in accordance with the literature. The data were assessed using percentage, average, standard deviation, chi-square and correlation analyses using SPSS 15.0 program package on computer. It was found that as the time the students used computer and internet increased, their success at school was more adversely affected, that the male students more actively used computers and internet, and negative opinions on use of computer and internet were at higher rates among students with low academic success levels. It was concluded that it will be useful if families keep the time for internet use by students under control, social activities are increased and group works are emphasized at schools, and thus social relations of teenagers are strengthened.