The aim of this study was to identify smoking cessation failure subgroups among Korean adolescents. Participants were 379 smoking adolescents who joined a smoking cessation program. A questionnaire and a cotinine urine test were administered before the program began. Three months after the program ended, the cotinine urine test was repeated. A decision-tree model identified seven subgroups with low or high smoking cessation rates. The predictors of smoking cessation were intention to stop smoking, initiation of smoking, amount of cigarette use, self-efficacy, and paternal smoking status. The subgroup with the lowest smoking cessation rate included adolescents who did not have any intention to stop smoking and who had started smoking after eighth grade, and none of the participants in this group stopped smoking. The results of this study provide crucial information for tailored smoking cessation programs.