We examined the occurrence and coexistence of externalising and internalising problem behaviour among Swedish boys and girls, and investigated whether there are differences in the accumulation of problems among adolescents with different behavioural, demographic and social characteristics. The results are discussed in the context of self-salience schemas. The source material comprised all ninth grade pupils in a province in central Sweden in 2008 (N = 3,095). First, girls were found to be more prone to experience internalising problem behaviour, whereas no sex differences were found regarding externalising problem behaviour. Second, multidimensional scaling maps indicated that, compared with boys, self-esteem and the PsychoSomatic Problem (PSP) scale among girls more closely indicated externalising problem behaviour components, whereas anxiety was situated far from the other externalising problem behaviour indicators. Finally, linear regression analyses indicated family type as the primary explanatory background factor for externalising problem behaviour and economic hardship as the primary explanatory background factor for internalising problem behaviour.