Background: Problematic use of internet (PUI) may have negative impacts on psychological distress and quality of life (QoL). This situation might be more profound in people with attention-deficit/hyperactivity disorder (ADHD) due to poorer behavioral control and regulatory capacity. However, there is little evidence regarding mediated effects in the associations between PUI, psychological distress, and QoL in people with ADHD. Aims: To investigate mediating effects of psychological distress in the associations of problematic smartphone use (PSPU), problematic use of social media (PUSM), and problematic gaming (PG) with QoL in individuals with ADHD. Methods and Procedures: PUI behaviors of participants with ADHD (n = 99) were assessed using the Smartphone ApplicationBased Addiction Scale, Bergen Social Media Addiction Scale, and Internet Gaming Disorder-Short Form. Psychological distress was assessed using the Depression, Anxiety, Stress Scale and QoL using the Kid-KINDL. Outcomes and Results: Psychological distress mediated the associations between PUI and different domains of QoL, except for selfesteem QoL. There were also positively direct effects between PG and physical QoL, PUSM and friends' QoL, and PSPU and physical QoL. Conclusions and Implications: PUI may associate with poor QoL in people with ADHD via psychological distress. Programs on reducing PUI for people with ADHD are needed.