BACKGROUND: One important aspect of the societal burden of mental disorders is the extent to which these problems cause disability. AIMS: To assess days out of role associated with commonly occurring mental disorders in comparison with physical disorders in Portugal. METHOD: National cross-sectional survey, with home interviews carried out with 3849 adult (aged 18+) respondents (57.3% response rate). RESULTS: Twelve-month prevalence for any mental disorder was 21.8%, any physical disorder 55.1% and any disorder 63.1%, with an average of 2.3 disorders per respondent with a disorder. Close to one out of every 10 respondents (9.2%) reported at least one day totally out of role in the past month (median of 6.4 days/any). The 18 conditions accounted for 78.2% of all days out of role, with 20.2% because of mental disorders and 59.2% because of physical disorders. CONCLUSIONS: Mental disorders account for a substantial proportion of all role disability in the Portuguese population. Early detection and intervention would have a positive societal effect. Owing to highly frequent comorbidity, simultaneous management of mental and physical disorder comorbidities is advised for greater effect.