Internet addiction (IA) has been reported as prevalent in adolescents with autism spectrum disorders (ASD) and attention-deficit hyperactivity disorder (ADHD). However, the course of IA in this population has not been elucidated. The authors performed a 2-year follow-up study including 89 out of 132 adolescents with ASD and/or ADHD in a psychiatric clinical setting who participated in the original cross-sectional study assessing IA prevalence. Within this sample of participants from both the original and the follow-up study, results showed a 2-year IA remission and incidence rate of 60% and 5%, respectively. Our findings imply that the course of IA in psychiatric populations with ASD and/or ADHD might be similar to reports from previous studies with general adolescent populations.