This study aimed at determining the impact of demographic factors on the Internet usage purposes of high school students. The population of the study consisted of students between 9th and 12th grades from the Anatolian high schools, science high schools, social sciences high schools, sports high schools and fine arts high schools in Turkey. The sample was chosen through the stratified and cluster sampling procedure. The students were chosen randomly depending on the regions of their school attendance. The sample for this research numbered 3170 students. The research was conducted in the second term of the 2014-2015 academic year. The data were obtained through online forms and the bases of participation are honesty, sincerity, and volunteerism. The data collection tool is a questionnaire and a demographic information form prepared by the researchers. Chi-square Automatic Interaction Detector (CHAID) analysis was conducted through SPSS in order to determine the demographic factors affecting the purposes of internet usage among high school students. The results of this research show that 9th grade students in Turkey mostly use the Internet to do homework while students from other grades mostly use the Internet for social networking. The male students use the Internet for playing video games more frequently in comparison with female students. Also, socioeconomic status affects the purpose of Internet usage. Hence it is suggested that teachers talking to male students might use the examples of computers and games and with female students they might relate the topics to social media.