Purpose The Dementia Questionnaire for People with Learning Disabilities (DLD) is one of the main screening and monitoring tools for dementia in people with Down’s syndrome (DS). As part of a quality improvement project to improve the care for people with DS and dementia in an intellectual disability service, the authors studied the screening and monitoring process by retrospectively investigating the use of DLD and exploring clinicians’ experience of using it. Design/methodology/approach DLDs completed in the service was retrospectively assessed. Changes in DLD scores were matched against people who received a clinical diagnosis of dementia. Data were analysed to estimate sensitivity, specificity and predictive values of DLD. A questionnaire was used to assess clinicians’ experience. Findings Data for 20 service users was collected. DLD cognitive scores showed 80% sensitivity and 60% specificity for the diagnosis of dementia, with a positive predictive value of 40% and negative predictive value of 90%. Staff found DLD to be easy to perform but time consuming. This led to the preparation of a decision tool for appropriateness of performing a DLD. Originality/value The results show that a negative DLD helps to exclude dementia where there is concern over cognitive decline, but a positive result is not specific enough to suggest the possibility of dementia. This shows that DLD may have limitations if used as a screening tool alone but could be used for the monitoring of the disease trajectory of those with a confirmed diagnosis as well as to establish a baseline DLD when a person is screened for dementia first.