Background: Advance care planning (ACP) is increasingly prominent in many countries; however, the evidence base for its acceptability and effectiveness is limited especially in conditions where cognition is impaired, as in dementia. Method: This qualitative study used semi-structured interviews with people with mild to moderate dementia (n = 17) and family carers (n = 29) to investigate their views about planning for their future generally and ACP specifically. Results: People with dementia and their families make a number of plans for the future. Most people undertook practical, personal, financial, and legal planning. However participants did not make formal advance care plans with the exception of appointing someone to manage their financial affairs. Five barriers to undertaking ACP were identified: lack of knowledge and awareness, difficulty in finding the right time, a preference for informal plans over written documentation, constraints on choice around future care, and lack of support to make choices about future healthcare. Conclusions: Health and social care professionals can build on people's preferences for informal planning by exploring the assumptions underlying them, providing information about the possible illness trajectory and discussing the options of care available. Health and social care professionals also have a role to play in highlighting the aspects of ACP which seem to be most relevant to the wishes and aspirations of people with dementia.