Introduction:In Mexico, efforts have been made to increase understanding of Alzheimer's disease (AD) and other dementias, as well as to improve the care of patients with these diseases and that of their caregivers. However, people's interest in making decisions and facing the ethical dilemmas regarding the possibility of living with mental diseases has not been investigated. Objective: To know the opinions of mature adults on some ethical dilemmas related to the possibility of living with AD or other dementias. Methods: Observational, cross-sectional, correlational study. Participants answered a self-administered questionnaire. Results: 134 mature adults answered the questionnaire; 70.9% had thought about the possibility of suffering from some dementia and the vast majority would like to know their diagnosis; approximately, half the participants had informed their families of their wishes about medical treatment in the future; 39.6% did not approve artificially feeding a patient who can no longer eat or decide; 37.3% did approve this. Conclusions: There is interest in advance decisions in the face of the possibility of suffering from dementia. To answer unanswered questions in this regard, it is important for research on the subject to continue, as well as to solve some ethical dilemmas and promote the use of advance directives.