This paper argues that some of the misunderstandings surrounding the meaning and function of the concept of human dignity in bioethics arise from a lack of distinction between two different roles that this notion plays: one as an overarching policy principle, and the other as a moral standard of patient care. While the former is a very general concept which fulfils a foundational and a guiding role of the normative framework governing biomedical issues, the latter reflects a much more concrete and context-specific understanding of the patient as a "person". The importance of dignity as a policy principle will be described by appealing to the distinction between principles and rules as developed by some legal philosophers. The value of dignity as a standard of patient care will be illustrated with the help of concrete examples and by drawing on the taxonomies of dignity proposed by Jonathan Mann and other scholars. The overall scope of the article is to highlight this double and complementary role of human dignity in bioethics.