Children and adolescents, misusing drugs and alcohol, are at significant risk of comorbidity. There is a significant association between attention - deficit disorder and conduct disorder, major depression and substance misuse. Familial traits and individual developmental experience further influence the incidence of comorbidity. Diagnostic tools, for the accurate identification of comorbidity, need further development. Treatment of comorbid conditions is complex. The evidence from the recent literature is of particular importance at this time as services for children and adolescents, either with substance misuse alone or comorbidity with psychiatric disorder, are scarce and urgently need to be developed.