A community survey of the common mental disorders in a geographically defined treatment service area was used to explore the socio-demographic correlates and service utilization of people with alcohol and drug use disorders living in the area. These data represent the most comprehensive data on substance use disorders in a defined geographic region in Australia. Alcohol and drug use disorders were most likely to be found in the young, with those aged 18-34 years being three times more likely to have an alcohol use disorder than those aged 55 years and over. A third (33%) of those people with an alcohol use disorder and 42% of those with a drug use disorder had consulted a health professional in the past 12 months for their substance use disorder.