Background Behaviour problems are common among individuals with intellectual disabilities (ID) especially in those with more severe forms. The determination of the functional profile of a targeted behaviour has important implications for the design of customised behavioural interventions. Method We investigated the relationship between the level of ID and the functional profile of aggression, stereotypy and self‐injurious behaviour (SIB) using the Questions about Behavioural Function (QABF). Two staff members at two time points completed the QABF for each of 115 adults with varying levels of ID participating in a day training and habilitation programme. Results and conclusions Our results suggest that there is a differential relationship between the functions of behaviour problems and level of ID. While SIB is more often seen by raters to be maintained by escape of social demands and by attaining access to tangible items with the decline of the intellectual level, aggressive and stereotypic behaviours were identified more often as serving multiple functions equally across functioning level.