Advance Declarations of Will, in their two usual forms, the living will and the appointment of a health care proxy, were expressly recognized in the Portuguese legal system with the approval of Law No. 25/2012 of 16 July 2012, which brought new challenges for the understanding of the legal system, namely by enshrining the institution of voluntary representation in health care.This is a mechanism of voluntary representation, which is traditionally reserved for the conclusion of legal transactions or the practice of other legal acts in place of the represented person. At a time when autonomy is increasingly valued, this instrument presents itself, in the first instance, as a useful mechanism for responding to a specific incapacity limited to the area of health.