An estimated 8.7% to 9.8% of school-age children in the United States have attention deficit hyperactivity disorder (ADHD), affecting 4.3 to 4.9 million public school students. ADHD is a costly disorder that often goes untreated, especially among adolescents. Accessible computer- based programs have emerged to address the neurocognitive deficits of ADHD, but results to date have been disappointing. In this study, we tested the acceptability, playability, and user satisfaction of a novel planning/organization skills training game, called "ATHEMOS," based on an established psychosocial treatment package (i.e., Challenging Horizons Program). We conducted eight focus groups during a three-year development period, using feedback from 72 young adolescents with ADHD to iteratively improve the game. Then, during a pilot study in the fourth year, we collected data from 16 young adolescents who played the game as part of a 6- to 16-week school-based intervention. Our findings suggest that the serious game resulted in acceptability and playability ratings only moderately below that of recreational games ([delta]= -0.40). Critically, average perceptions remained positive when delivered within a school-based ADHD intervention over several weeks or months, with strong overall user satisfaction. Boys found the game more acceptable than girls, with ratings near that of recreational games ([delta] = -0.23). We conclude that computer-assisted behavior interventions appeal to adolescents with ADHD and offer a potentially promising treatment delivery method in schools.