Objective: To assess the effect of attention-deficit/hyperactivity disorder (ADHD) and its treatment on growth outcomes in children followed into adulthood. Study design: Two identically designed, longitudinal, case-control studies of males and females with and without ADHD were combined; 124 and 137 control and subjects with ADHD, respectively, provided growth information at the 10- to 11-year follow-up. We used linear growth curve models to estimate the effect of time on change in height and whether this effect differed by sex and ADHD status. We also examined the effect of stimulant treatment on growth outcomes. Results: We found no evidence that ADHD was associated with trajectories of height over time or differences at follow-up in any growth outcomes. Similarly, we found no evidence that stimulant treatment was associated with differences in growth. However, among subjects with ADHD, major depression was associated with significantly larger weight in females and smaller height in males. Conclusions: Our results do not support an association between deficits in growth outcomes and either ADHD or psychostimulant treatment for ADHD. These findings extend the literature on this topic into young adulthood and should assist clinicians and parents in formulating treatment plans for children with ADHD.