This paper discusses theoretical models for understanding dementia and how these are emerging in the formation and development of dementia care policy across the UK. Dementia attracts multi-disciplinary and multi-professional questions and responses. Three broad theoretical models underpin dementia care policy (as well as practice and research): biomedical, psycho-social and social-gerontological. These are critically assessed and discussed in relation to illustrative examples of dementia policy across three policy regions of the devolved UK. The contribution and implications of theoretical models of dementia policy highlight the importance of recognising how different theoretical understandings of dementia influence dementia policy. The development and improvement of policy and practice in the area of dementia care require an understanding of the often implicit theoretical approaches to dementia.