Background: Antisocial behaviour is often comorbid with depressed mood but is itself a collection of heterogeneous behaviours. Using a genetically informative design, we examine heterogeneity in antisocial behaviour and overlaps between different forms of antisocial behaviour with depressed mood. Methods: Data were drawn from the G1219 large-scale community sample containing self-report questionnaire data from 941 twin pairs and 328 sibling-pairs aged 12-21 years. Results: Inter-correlations among oppositionality, physical aggression and delinquency, and between the antisocial subscales and depressed mood, were mediated by genetic and non-shared environmental influences. Genetic factors generally contributed more to the correlations than the non-shared environment. Conclusions: These results indicate that many genetic and non-shared environmental influences were common to all the traits studied, but there was also evidence for trait-specific effects.