The purpose of this study is to analyze the interaction between self-related health (SRH) and physical activity, sedentary behavior, smartphone usage time, and sleep time in Korean adolescents. The data used for the analysis was the 2021 Korea Youth Risk Behavior Web-Based Survey, and the subjects of the study were 54,848 middle and high school students nationwide. IBM SPSS Statistics 27.0 for Windows was used for data analysis, and the significance level is set at   . In the analysis by sex, a binary logistic regression analysis was conducted, with dependent variables as SRH, monthly age and household economic status, and academic performance as covariates, and independent variables as physical activity time, sedentary time, smartphone usage time, and sleep time. The dependent variable SRH was reclassified into two groups, healthy and non-healthy, and the estimates of the odds ratio of each factor, 95% confidence intervals, and p values for the odds of 'good SRH' were obtained. As a main result, the only independent variable that effectively affects SRH of adolescents was physical activity. These results are different from several previous studies, and it is believed that the limitations of the study should be supplemented as a follow-up task in the future. There is a need to consider not only the cross-sectional analysis conducted in this study but also the longitudinal analysis.