Purpose: This study was conducted to identify the degree of Internet addiction and factors influencing this addiction among high school students in Korea. Method: A total of 405 high school students in the Gyeoung-gi, Daegu and Gyeoung-buk areas were surveyed using questionnaires for data collection. Results: Internet addiction among high school students in Korea was relatively low. In the overall ratio distribution, however, the students who were classified as either addicted or at risk of addiction accounted for a high percentage of the students, 31.1%. Positive or negative relationships were found between internet addiction and the research variables but multiple regression analysis revealed that the most powerful predictor of Internet addiction was depression. Conclusion: Using the above results, it is necessary to develop Internet addiction prevention programs for adolescents. There should be a more comprehensive study in the future for an in-depth understanding of internet addiction of adolescents.