Social networking services (SNS) addiction and the SNS use motives have been known to differ by gender. However, no previous study has comprehensively examined the relationships among gender, SNS use motives, and SNS addiction in Korean adolescents. This study investigated gender differences in SNS addiction tendencies and SNS use motives among 277 adolescents aged 13 to 18, and further analyzed which SNS use motives predicted SNS addiction tendency in girls and boys. Participants completed the SNS Addiction Proneness scale (SNSAP) and the SNS Use Motives Scale (SUMS). It was found that girls exhibited significantly higher SNS addiction tendencies than boys, and also scored significantly higher in social motive and conformity motive. Additionally, The conformity motive significantly predicted SNS addiction tendencies in boys, while the coping motive significantly explained addiction tendencies in girls. These findings suggest that both SNS addiction and SNS use motives may differ by gender among Korean adolescents, indicating the need for gender-specific intervention to prevent and treat SNS addiction.