The present study examined associations between boys' and girls' self-reported psychological adjustment and a wide spectrum of peer-rated behaviours in the school context using a sample of 463 Estonian early adolescents (M[subscript age] = 12.90). Although girls had more internalised problems and boys more externalised problems, the associations between adolescents' psychological adjustment and behaviour were not gender-specific. Among both boys and girls, hostility was positively associated not only with their peer-reported misbehaviour, but also with sociable behaviour and negatively with studiousness. Adolescents with negative self-esteem were perceived to exhibit high levels of self-centred competitive behaviour, misbehaviour and also sociable behaviour. Those with negative self-adequacy, on the contrary, were less likely to behave in a self-centred competitive and sociable manner. In general, the findings show that psychological maladjustment may appear not only in well-observed problematic behaviour but also in seemingly ordinary behaviour in school.