Objective: ADHD and sleep-disordered breathing are both prevalent in adulthood. Because both conditions may be responsible for similar symptoms of cognitive impairment, the authors investigate whether their presentation may overlap in adults diagnosed with ADHD. Method: Data are collected from six adults with sleep complaints who were diagnosed with ADHD using rigorous clinical criteria. All participants undergo overnight polysomnography and complete questionnaires about sleep quality, circadian sleep pattern, and daytime fatigue. Results: On standardized measures, all participants report poor sleep quality, two report daytime fatigue, and none report distinct deviation from normal sleep and wake cycle pattern. Polysomnography reveals evidence of sleep-disordered breathing and sleep fragmentation in all participants. Conclusion: Objective evidence of breathing-related sleep disorders can be found in some adults with carefully diagnosed ADHD who report sleep complaints. This report highlights the importance of identifying treatable sleep disorder comorbidity in adults with ADHD. (Contains 3 tables.)