The purpose of this study is to examine the associations among attention deficit/hyperactivity, social withdrawal, peer relationships, and depression in early adolescence. Gender differences in the associations were also examined. This study investigated these relationships and the gender differences using structural equation modeling multi-group analysis. The third wave data from Korea Children and Youth Panel Survey (KCYPS) of fourth graders were analyzed. The results indicated that attention deficit/hyperactivity had significant effects on depression directly and indirectly through social withdrawal and peer relationships. These results suggest that new programs should be developed to prevent or alleviate depression associated with attention deficit/hyperactivity among adolescents. Specifically, social withdrawal and peer relationships need to be emphasized in planning prevention or intervention programs to promote mental health of adolescents with attention deficit/hyperactivity.