This study was done to identify the difference between internet usage levels and health behaviors of adolescents in Korea. Data from the Korea Youth Risk Behavior Web-based Survey 2009 collected by the Korean Center for Disease Control were analyzed using χ2-test. The potentially dangerous group was 11.9%, and high-risk group was 3.1%. Difference in internet usage levels according to general characteristics were as follows. : gender, school, school record, parental living arrangement, level of father's education, level of mother's education, and economic status. And difference in internet usage levels according to health behavior related factors were as follows. : lifetime smoking, current smoking, lifetime drinking, current drinking, lifetime drug, current drug, sexual intercourse, subjective sleep time satisfaction, subjective health status, strenuous exercise practice(3days/week), stress level, depression, suicidal thinking, and suicidal attempt. The findings suggest that board intervention programs should be provided to prevent problem of internet addiction.