Study of the quality and use of patient-based outcomes instruments has been and still is an area of growing interest in many health disciplines, including nursing. In the last 30 years, the number of measures has greatly increased. However, there is enormous disparity in their contents, hampering selection of one or other of these instruments for use in clinical medicine or research. The aim of this article was to describe the quality attributes that patient-based health instruments should meet before being used. For that purpose, we provide a detailed description of the attributes on which there is both national and international consensus. These instruments are grouped in 3 main axes: conceptual adequacy, applicability, and psychometric properties.