This study presents national data on the comparative role impairments of common mental and chronic medical disorders in the general population. These data come from the National Comorbidity Survey Replication, a nationally representative household survey. Disorder-specific role impairment was assessed with the Sheehan Disability Scales, a multidimensional instrument that asked respondents to attribute impairment to particular conditions. Overall impairment was significantly higher for mental than chronic medical disorders in 74% of pair-wise comparisons between the two groups of conditions, and severe impairment was reported by a significantly higher portion of persons with mental disorders (42.0%) than chronic medical disorders (24.4%). However, treatment was provided for a significantly lower proportion of mental (21.4%) than chronic medical (58.2%) disorders. Although mental disorders were associated with comparable or higher impairment than chronic medical conditions in all domains of function, they showed different patterns of deficits; whereas chronic medical disorders were most likely to be associated with impairment in domains of work and home functioning, mental disorders were most commonly associated with problems in social and close-relation domains. Comorbidity between chronic medical and mental disorders significantly increased the reported impairment associated with each type of disorder. The results indicate a serious mismatch between a high degree of impairment and a low rate of treatment for mental disorders in the United States. Efforts to reduce disability will need to address the disproportionate burden and distinct patterns of deficits of mental disorders and the potentially synergistic impact of comorbid mental and chronic medical disorders.