El asunto cardinal de las Advance Directives o Declaraciones Anticipadas de Tratamiento Medico radica en determinar la eficacia y validez de la voluntad conferida mediante el consentimiento informado suscrito en estado de capacidad, que tiene como finalidad interpretar la intencion del individuo para un momento futuro en el cual estara en estado de incapacidad para tomar decisiones en cuanto a los tratamientos y disposiciones medicas. Existen lineamientos diferenciadores de las Advance Directives entre los sistemas common law y civil law , que deben ser identificados para comprender la legislacion y la praxis juridica que las contemplan, y para abordar un estudio comparado de este instituto en la cultura juridica occidental. Las Advance Directives han sido confundidas con la acepcion ‘Testamento Biologico’ por errada duplicacion legislativa. En el imaginario colectivo las consecuencias de las Advance Directives coinciden con la eutanasia, sobre todo en la modalidad pasiva mas que en la activa. Asi, son en realidad dos conceptos diferentes, con conexiones estrechas, pero con distinta reglamentacion legal, a tal punto que en Europa Continental las Advance Directives son admitidas y hacen parte de la realidad social, al contrario de la eutanasia, que es excluida legislativamente y que tiene amplia aceptacion en el sistema del common law . The main issue of Advance Directives is determining the effectiveness and validity of the will conferred by the informed consent signed in capacity, which aims to interpret the intent of the patient for a future time in which he will be in a state of inability to decide on treatments and medical provisions. There are guidelines that differentiate Advance Directives in common law and civil law systems, which must be identified in order to understand the law and legal practices that relate to them and to address a comparative study of this institution in Western legal culture. Advance Directives have been confused with the living will, because of a mistaken duplication of legislation. In the collective imagination the consequences of Advance Directives coincide with euthanasia, especially in the passive rather than in the active mode. However, these are two different concepts, with close connections, but with different legal regulation, to such an extent that Continental Europe accepts Advance Directives, and they are part of society, as opposed to euthanasia, which is excluded legislatively, although it has wide acceptance in common law systems.