With widespread use of the smartphone, clinical evidence for smartphone addiction remains unclear. Against this background, we analyzed the effect of smartphone use patterns on smartphone addiction in Korean adolescents. A total of 370 middle school students participated. The severity of smartphone addiction was measured through clinical interviews and the Korean Smartphone Addiction Proneness Scale. As a result, 50 (13.5%) were in the smartphone addiction group and 320 (86.5%) were in the healthy group. To investigate the effect of smartphone use patterns on smartphone addiction, we performed self-report questionnaires that assessed the following items: smartphone functions mostly used, purpose of use, problematic use, and parental attitude regarding smartphone use. For smartphone functions mostly used, the addiction group showed significantly higher scores in “Online chat.†For the purpose of use, the addiction group showed significantly higher “habitual use,â€â€œpleasure,â€â€œcommunication,â€â€œgames,â€â€œstress relief,â€â€œubiquitous trait,†and “not to be left out.†For problematic use, the addiction group showed significantly higher scores on “preoccupation,â€â€œtolerance,â€â€œlack of control,â€â€œwithdrawal,â€â€œmood modification,â€â€œconflict,â€â€œlies,â€â€œexcessive use,†and “loss of interest.†For parental attitude regarding children's smartphone use, the addiction group showed significantly higher scores in “parental punishment.†Binary logistic regression analysis indicated that “female,â€â€œuse for learning,â€â€œuse for ubiquitous trait,â€â€œpreoccupation,†and “conflict†were significantly correlated with smartphone addiction. This study demonstrated that the risk factors for smartphone addiction were being female, preoccupation, conflict, and use for ubiquitous trait; the protective factor was use for learning. Future studies will be required to reveal the additional clinical evidence of the disease entity for smartphone addiction.