Using data from an ongoing longitudinal study of adolescent drug use, this study examines the proportion of teenagers living with parents who are problem alcohol or drug users. Around two per cent of parents report high levels of problem drinking and one per cent report problem drug use. If a broader definition of hazardous drinking is used, the proportion of teenagers exposed increases to over 15 per cent. When substance use is examined at a family level (taking account of alcohol and drug use amongst dependent children in addition to that of parents), the proportion of families experiencing some form of substance use is considerable. These findings add further support to the call for increased recognition of the needs of dependent children within adult treatment services when working with parents. Likewise, the reduction of harm to children as a result of parental substance use should be an increasingly important priority for family support services. This is likely to be achieved through the closer integration of addiction and family services. Copyright © 2008 John Wiley & Sons, Ltd.