Objective: ADHD is associated with poor functional outcomes. The objectives were to investigate the prevalence of functional impairment and occupational status in a clinically referred sample of adults with ADHD and explore factors predicting occupational outcome. Method: A sample of 149 adults with a confirmed diagnosis of ADHD participated in the present study. Cross-sectional data were collected from the participant's medical records and from self-report questionnaires. A multiple regression model was applied to identify possible predictors of occupational outcome. Results: Only 22.2% had ordinary work as their source of income, compared with 72% in the general population. The most prevalent comorbid disorders were lifetime depression (37.8%), substance abuse (28.1%), and alcohol abuse (23.3%). Age at first treatment with central stimulants and inattentiveness negatively predicted occupational outcome. Conclusion: Adult ADHD was associated with lower educational attainment and lower level of employment. Later age of first central stimulant treatment and higher inattentiveness ratings were associated with lower level of employment. (Contains 3 tables and 1 figure.)