Studies conducted outside of Scandinavia indicate that most adolescents with substance misuse problems suffer from co-morbid mental disorders. The present study assessed the mental health of adolescents seeking help for substance misuse problems in a large Swedish city. Parents' mental health was also examined. The sample included 97 girls with their 90 mothers and 52 fathers, and 81 boys with their 72 mothers and 37 fathers. The adolescents completed a diagnostic interview, either the Kiddie-SADs or the Structured Clinical Interview for DSM-IV (SCID) depending on their age. Their parents underwent diagnostic interviews with the SCID. Ninety per cent of the girls and 81% of the boys met criteria for at least one disorder other than substance misuse, and on average, they suffered from three other disorders, most of which had onset before substance misuse began. Almost 80% of the mothers and 67% of the fathers met criteria for at least one mental disorder other than alcohol and drug-related disorders. The findings concur with those reported from studies conducted in North America. The results suggest that in Sweden mental disorders are not being identified and effectively treated among some children and young adolescents who subsequently abuse alcohol and/or illicit drugs. Adolescents who consult for substance abuse problems require assessments and treatment by mental health professionals.