Objectives: This study aimed to examine the moderating effects of callous-unemotional traits in the relationship between adolescents' ADHD subtypes and cyberbullying perpetration. Methods: The participants included 457 students (184 boys; 273 girls) in the 1st~3rd grade in middle school living in Gyeonggi-do. They completed questionnaires on ADHD Diagnostic Scale, Inventory of Callous-Unemotional Traits Scale, Cyberbullying Perpetration Scale. The study applied correlation analyses, and hierarchical regression analyses using SPSS 23.0. In addition, graphical analyses and simple slope analyses were conducted. Results: The results indicated that adolescents' hyperactivity/impulsivity level positively increased cyberbullying perpetration level. In addition, callous-unemotional traits showed a significant moderating effect in the relationship between adolescents' inattention and cyberbullying perpetration. Conclusions: Adolescents with high inattention and high callous-unemotional traits exhibited more severe aggressive behavior in the cyberspace. The results indicated that callous-unemotional traits are a risk factor in the relationship between inattention and cyberbullying perpetration.