Executive dysfunction is very broad term used to capture a range of interacting high-level cognitive, emotional and behavioural difficulties, commonly seen after acquired brain injury (ABI). Many argue that the concept of executive functioning should be subdivided into several separate dimensions. In this study we explore the dimensional structure of a tool designed to assess level of executive functioning, the Dysexecutive (DEX) Questionnaire (Burgess, Alderman, Wilson, Evans, & Emslie, 1996), in order to inform theoretical conceptualisations of executive functioning and improve measurement precision in rehabilitation centres. Rasch analysis was undertaken on the responses of 363 people with ABI to the DEX. Overall, the questionnaire did not perform as a unidimensional, interval-level scale of executive functioning, suggesting that it measures more than one psychological construct. Most subscales previously proposed using factor analysis, including those suggested in the DEX manual, did not perform as unidimensional interval-level scales either. Several new subscales in keeping with theoretical conceptualisations of the different dimensions of executive functioning are proposed, alongside suggestions for revision of the wording and scoring of some of the items in the DEX. These results provide a platform for future evaluation of executive function rehabilitation programmes.