OBJECTIVE: We evaluated the driving skills of teenagers with attention deficit hyperactivity disorder (ADHD) during simulated driving before starting driving lessons and observed whether methylphenidate (MPH) affected their performance. METHOD: Sixty teenagers ages 15-18 yr were included; 29 teenagers with ADHD were tested with and without MPH, and 31 teenagers (control group) were tested once. All participants were tested on the STISIM Drive™ simulator. RESULTS: The number of center-line crossings was higher in the group without MPH treatment than in the control group and the MPH-treated group. The group without MPH treatment had more road-edge excursions compared with the control group and drove faster than the MPH-treated group. CONCLUSION: Adolescents with ADHD without MPH treatment demonstrated impaired performance more often while driving the simulator, resembling characteristics found during on-road driving among teenagers with ADHD. Trainer awareness is a primary intervention before taking driving lessons to help teenagers achieve safe driving performance.