An association between overweight and attention-deficit/hyperactivity disorder (ADHD) in children was previously suggested. We examined the prevalence of overweight, anthropometric changes, and the effect of methylphenidate treatment in 275 children with ADHD without neurological comorbidities and in controls. Data were extracted from medical charts, for up to 17 months of follow-up. Height, weight, body mass index, and their z scores did not differ between the ADHD and control groups. Prevalence of overweight and obesity was lower in the ADHD group compared with controls (19% vs 35%, P = .02, and 7% vs 16%, P = .05, respectively). During a follow-up of up to 17 months, no significant changes in height or body mass index z scores were found, including in a subgroup of overweight children. We conclude that compared with local controls, children with ADHD have rates of overweight and obesity that are lower, but that are similar to national estimates. Methylphenidate treatment did not significantly affect height, weight, or overweight status.