As life expectancy increases for people with learning disabilities, the impact of dementia on people with learning disabilities and their families, carers and services is becoming more apparent. Psychological services for learning disabilities are receiving an increasing number of referrals requesting dementia assessment. Health and social care services are adapting to the diverse needs of an ageing population with learning disabilities. This article describes a study investigating the relationship between two assessments for dementia in people with learning disabilities. Carers of people with learning disabilities over the age of 50 (or 40 if the individual had Down syndrome) completed the Dementia Questionnaire for Mentally Retarded People and the Adaptive Behaviour Scale–Residential and Community. Overall, the two questionnaire measures showed significant relationships. However, results suggested that both assessments have clinical value in informing individual needs and aiding diagnosis. Implications for both clinical and social care services are discussed.