To compare gambling behaviors in a random sample of community residents with and without mental disorders identified by the Composite International Diagnostic Interview (CIDI). A large national community survey conducted by Statistics Canada included questions about problems arising from gambling activities as per the Canadian Problem Gambling Index (CPGI). We compared respondents within three gambling severity categories (non-problem, low severity and moderate/high severity gambling) across three diagnostic groupings (mood/anxiety disorders, substance dependence/harmful alcohol use, no selected psychiatric disorder). Of the 14,934 respondents age 18-64 years who engaged in at least one type of gambling activity in the previous 12 months, 5.8% fell in the low severity gambling category while 2.9% fell in the moderate/high severity category. Females accounted for 51.7% of the sample. The risk of moderate/high severity gambling was 1.7 times higher in persons with mood or anxiety disorder compared to persons with no selected disorder. For persons with substance dependence or harmful alcohol use, the risk of moderate/high severity gambling was 2.9 times higher. Persons with both mood/anxiety and substance/alcohol disorders were five times more likely to be moderate/high severity gamblers. The odds ratio for females was 0.6 and for those with less than post-secondary education it was 1.52. Differences in age and personal income were not significant. Individuals in the community suffering from mood/anxiety disorders and substance dependence/harmful alcohol, and especially those with both, experience a higher risk for gambling problems. The treatment of these comorbidities should be integrated into any problem gambling treatment program.