Background: We compared responsiveness to two self-report assessments of loneliness: the "UCLA Loneliness Scale" (UCLALS) designed for the general community, and the "Modified Worker Loneliness Questionnaire" (MWLQ) designed for people with intellectual disability (ID). Methods: Participants were 56 older adults with disability--40 individuals with ID and 16 without ID. They were individually assessed on the MWLQ and the UCLALS. The difficulty of the items in both scales was evaluated in relation to readability, features of question wording, question length and response format. Results: The UCLALS was more difficult than the MWLQ on each of the difficulty dimensions assessed. There was significantly greater responsiveness to the MWLQ than the UCLALS, especially among people with ID. Conclusions: To enable as many people with ID as possible express their views on loneliness, the ID-specific MWLQ is a much better choice. However, this choice comes at the cost of ready comparison to loneliness data for the general community, which is available for widely used assessments such as the UCLALS.