This diploma deals with the health care proxy, with regard to the general law (§§ 1002 ff ABGB). All characteristics of this juristic subject are compared to the rules of agency law. Because of the few explicit rules regarding the health care power of attorney, the existing loopholes can be filled by analogy with the right of representation but its protective nature, also suggests an analogy with custodianship. Practical problems, like the acceptance of the health care power of attorney in authority issues or self-contracting, are being discussed. In the first chapters, the effective beginning of the authorization is being reconsidered, for example the necessary formality or the legal competence. Afterwards, the scopes and limits of authorization contracts are being outlined. Then, the rights and duties of both, constituent and assignee, are being discussed. Finally the possibilities of termination are being presented.