Background: There is a need for assessments of psychological difference and disorder in people who have more severe intellectual disability (ID). Hyperactivity and impulsivity are two behavioural domains of importance as they are correlated with self-injury and aggression and this alludes to a shared cognitive correlate of compromised behavioural inhibition. Additionally, compromised behavioural inhibition is demonstrably related to repetitive behaviour and the latter might be expected to be associated with impulsivity and hyperactivity. Methods: The Activity Questionnaire (TAQ) was developed for this study. Three sub-scales with high levels of face validity were supported by factor analysis of the scoring of 755 intellectually disabled participants on the TAQ items. These sub-scales mapped onto the constructs of Overactivity, Impulsivity and Impulsive Speech. Test-retest, inter-rater reliability and internal consistency were robust. TAQ scores and scores on the Repetitive Behaviour Questionnaire (RBQ) were collected for a sample of 136 participants with varying degrees of ID. Results: Scores on the TAQ at sub-scale and full-scale level were not related to level of adaptive functioning. There were significant positive associations between overactivity (TAQ) and stereotyped behaviour (RBQ), impulsivity (TAQ) and restricted preferences (RBQ), and impulsive speech (TAQ) and repetitive speech (RBQ). Conclusions: The TAQ is a reliable assessment of hyperactivity and impulsivity for people with ID with robust factor structure. Validity requires evaluation. The relationship between impulsivity and restricted preferences may result from a common cognitive impairment in inhibition, which may underpin these two classes of behaviour. (Contains 6 tables and 3 footnotes.)