Recent research suggests that higher Body Mass Index (BMI) may be associated with ADHD diagnosis and greater ADHD symptom severity, but results have been inconsistent. Emerging research indicates that failure to account for age, sex, and medication status may contribute to discrepant results. In addition, the relationships to specific symptom domains (inattention, hyperactivity-impulsivity) require further examination. The current study uses a large, well-characterized cohort of individuals with and without ADHD to characterize the relationship between ADHD symptoms and BMI in both males and females.