We conducted a cross-sectional survey of a random sample of 1943 spouses of home-dwellers with Alzheimer's disease (AD) to examine the prevalence of court-appointed guardians or financial powers of attorney for persons with AD, related factors and the need for information about these issues among caregiving families. The questionnaire consisted questions on variables of demographic characteristics, disability, symptoms and care needs of the person with dementia, the strain of caregiving, the use of court-appointed legal guardians or powers of attorney, as well as discussions about these issues -- and the need for them -- with a doctor. The response rate was 77% and the mean ages of those with AD and caregivers were 80.2 and 78.2 years, respectively. The use of legal guardians was rare (4.3%), while the use of financial powers of attorney was more common (37.8%). Only 9.9% of the couples had discussed these issues with their doctor, whereas 47.9% expressed a need for it. The factors associated with the use of these legal arrangements were related to the severity of dementia, including experiencing dementia symptoms for more than 3 years, poor functioning, incontinence and behavioural symptoms. There is a clear need for information on medico-legal issues related to dementia among caregivers of AD patients. If held soon after the diagnosis, such discussions could support the autonomy of these persons in spite of AD and enable them to plan for the future as they wish.