Objective: The objectives of this study were to investigate the relationships between ADHD symptoms and specific domains of the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36) mental component. Method: A sample of 149 adults participated in the study. Data were collected from the participant’s medical records and from self-report questionnaires. Multiple regression analyses were applied to identify predictors of the SF-36 mental component outcomes. Results: The sample was highly impaired in terms of low health-related quality of life on all SF-36 mental component scales. The ADHD Self-Report Scale (ASRS) inattentiveness was the strongest predictor of vitality and the only significant predictor of role-emotional outcome. The ASRS hyperactivity/impulsivity was the strongest predictor of social function and the only predictor of mental health outcome. Conclusion: Inattentiveness and hyperactivity/impulsivity were differentially related to specific quality-of-life domains. Inattentiveness was significantly predicting vitality and role-emotional outcomes, and hyperactivity/impulsivity predicted social function and mental health outcomes.