People who have been diagnosed with dementia, or who are worried that they may develop dementia in the future, are often concerned about how decisions regarding their medical treatment might be made should they lose the ability to decide for themselves. They may fear that life-sustaining or life-prolonging treatments would be provided long after they were able to achieve a level of recovery, length of life or quality of life that the person would at present consider to be acceptable or tolerable. The Mental Capacity Act 2005 gives people in England and Wales a statutory right to refuse treatment through the use of an 'advance decision'. An advance decision allows a person to state what forms of treatment they would or would not like should they become unable to decide for themselves in the future. The Alzheimer's Society is in support of the idea of advance decisions because they enable people with dementia to have a say in their future care. This document explains what an advance decision is and what it can and cannot do. It also provides practical advice and a downloadable form to draft an advance decision.