Objective: ADHD is associated with significant functional impairment in adults. The present study examined functional outcomes following 6-month double-blind treatment with either atomoxetine or placebo. Method: Patients were 410 adults (58.5% male) with "DSM-IV"--defined ADHD. They were randomly assigned to receive either atomoxetine 40 mg/day to 80 mg/day (n = 271) or placebo (n = 139). The primary functional outcome measure was the Endicott Work Productivity Scale (EWPS), and the secondary measure was the Adult ADHD Quality of Life (AAQoL). Patients were seen for four visits in 6 months. Results: At 6 months, both groups had nonsignificantly different improvements in EWPS total scores. Atomoxetine-treated patients showed significantly greater improvement than placebo-treated patients on the AAQoL after controlling for baseline severity of ADHD. Both treatment groups had low 6-month study completion rates. Conclusion: Following 6-month treatment with atomoxetine, adults with ADHD showed significantly greater improvement in functioning on disease-specific measures of quality of life than patients treated with placebo.