Objective: To determine the effects of symptom profile, comorbid psychiatric problems, and treatment on occupational outcome in adult ADHD patients. Method: Adult ADHD patients (N = 414) responded to questionnaires rating past and present symptoms of ADHD, comorbid conditions, treatment history, and work status. Results: Of the patients, 24% reported being in work, compared to 79% in a population-based control group (N = 359). Combined subtype of ADHD, substance abuse, and a reported history of depression or anxiety were correlated with being out of work. Current and past medical treatment of ADHD was correlated with being in work. Logistic regression analyses showed that stimulant therapy during childhood was the strongest predictor for being in work as adults (odds ratio = 3.2, p = 0.014). Conclusion: Early recognition and treatment of ADHD is a strong predictor of being in work as an adult, independently of comorbidity, substance abuse, and current treatment. (Contains 1 figure and 3 tables.)