In data from two cohorts of urban adolescents, measures of coping through support-seeking from peers and adults were related to indices of cigarette smoking and alcohol use. Peer support was positively related to substance use, whereas parental and other adult support were inversely related to substance use. Peer support had interactive relationships (positively weighted) with peer smoking and alcohol use: support had no effect when there were no friends who smoked/drank but had an increasingly greater effect for higher levels of peer smoking/drinking. Adult support had a similar (negatively weighted) interactive effect in relation to peer smoking and alcohol use. Peer and adult support interacted, with an increasingly greater effect of peer support on substance use for subjects with lower levels of adult support. Interactions with gender indicated peer support more strongly related to substance use for females than males. Implications for the theory of social networks and the prevention of substance use are discussed.