Smoking and drinking habits were studied among 1098 14-15-year-old adolescents using a mailed questionnaire. The subjects were drawn from a representative population of 5813 randomly selected 8-year-old children previously studied in the National Epidemiological Child Psychiatry Study in Finland in 1989. The questionnaire included items on the adolescents' smoking habits and alcohol consumption. Regular smoking was more common among boys (and girls) who, in childhood, had been rated by their parents (Rutter Parent Questionnaire) (RA2) as disturbed, 14.6% (30.3%), than among the nondisturbed, 6.6% (8.4%). Similarly, more of the previously disturbed (according to the RA2) adolescent boys drank alcohol regularly, 19.7%, as compared to the nondisturbed boys, 9.3%. Among girls, regular alcohol consumption was more common among those who previously had behavioural or mixed type problems (according to the RA2), 70.7%, as compared to those who previously had emotional or no problems, 12.2%. More of the previously depressed girls smoked regularly, 45.1%, than those who had not been depressed, 7.9%. Behavioural and emotional problems in childhood seemed to predispose to smoking and drinking in adolescence. The parents were more sensitive than the teachers in recognising the long-lasting problems of their children.