We utilized qualitative methodology to characterize potential long-term effects (therapeutic and iatrogenic) of behavior therapy for adolescents with ADHD. Forty-two in-depth interviews were conducted with adolescents with ADHD and parents, 4 years post-treatment. Grounded theory methods identified and reported prevalence of themes. All reported long-term effects were classified as benefits; no iatrogenic effects were noted. Long-term impact themes reported for a majority of participants included: development of organization skills (81.0%), enhanced motivation (57.1%), improved self-awareness (57.1%), improved parental knowledge of ADHD (76.2%), increased parent autonomy granting (61.9%), enhanced parental engagement with the youth (52.4%), and improved parent-teen relationships (52.4%). Fourteen themes were present for smaller subsamples, including reduced need for medication (3 of 9 medicated participants). Experimental studies of behavior therapy for adolescent ADHD should measure themes detected herein and directly test the possibility of long-term treatment effects.