There is an increasing emphasis on the importance of research having an impact on policy and practice. This can be more difficult to evidence in intellectual disability services because of the wide range of stakeholders involved. We evaluated whether an impact questionnaire covering: knowledge production, capacity building, informing policy and practice, social and economic benefits could successfully be used to evaluate the impact of research into and use of two screening questionnaires: the Learning Disability Screening Questionnaire (LDSQ) and Child and Adolescent Intellectual Disability Screening Questionnaire (CAIDS-Q). We conducted an online search for published peer reviewed and grey literature, and Internet resources that referenced LDSQ and/or CAIDS-Q. The resultant literature and resources were assessed for relevance and organized according to the categories outlined in the impact questionnaire. Evidence was found for all the areas of impact, with the largest body of evidence being in relation to informing policy and practice and social benefits and the least for economic benefits. The impact questionnaire provided the basis for a comprehensive and useful evaluative framework to assess impact, although there was some overlap between the different categories. The process of using it highlighted some wider issues to consider when attempting to evaluate impact. The results indicated that the research underpinning the LDSQ and CAIDS-Q had resulted in significant, generally positive, and wide-reaching impact on policy and practice in intellectual disability and other services, resulting in a number of positive outcomes.