Objective: Some studies show an association between ADHD and impaired balance/gait in children. However, it remains largely unexplored whether such an association exists in adults. We explore that association in this study. Method: This cross-sectional study included 45 adults aged 17 to 21 (25 with, and 20 without ADHD), most obtained from a longitudinal cohort study beginning in childhood. We measured balance/gait using objective measures from inertial sensors during the Instrumented Stand and Walk Test. Demographics and severity of ADHD symptoms were measured via questionnaires. Results: Young adults with ADHD showed a tendency toward worse balance and impaired gait in a dual-task activity than adults without ADHD. Conclusion: These findings suggest balance and gait impairments are associated with ADHD in young adults. Balance/gait measures may hold promise as markers for persistent neurodevelopmental disorders, and the novel task used here may hold promise for measuring these impairments in adults with ADHD.