Purpose: The purpose of this study was to identify the agreement between the perception of usage of smartphones and the resulting levels of addiction. Methods: A total of 400 subjects from schools in Busan were enrolled through convenience sampling: the sixth grade of elementary school, middle school, academic and specialized high school students; 100 from each group. The data were collected from June 20 to July 20, 2013. Part of the questionnaire collected 400 questionnaires, 6 unsatisfactory were excluded. The data were analyzed by descriptive statistics, chi-square test and Cohen’s kappa using SPSS win 18.0 program. Results: First, as a result of examining the level of smartphone addiction, high-risk and potential-risk groups constituted more than 20% of the total subjects: it was confirmed that the potential-risk group increased rapidly after middle school and showed the highest rate of the high-risk group in high school students. Second, the results of the subjective perception portion of the questionnaire related to the usage of smartphones among adolescents showed that more than half of students did not consider themselves addicted to smartphones. Lastly, agreement between the perception of one''s own smartphone addiction and real level of addiction was moderate. Perception of addiction for 2/3 of the total concurred with actuality, while approximately 15% of the normal-user group and 30% of the risk group perceived their statuses incorrectly. Especially middle school students showed the lowest agreement. Conclusion: Based on the finding of this study, health education should teach adolescents especially, middle school students to have an appropriate and realistic value about smartphones in order to gratify the demands of their times. Consequently, developing diversified intervention programs focusing on step-by-step methods to reduce addiction of smartphone is suggested.