The chapter aims to provide a classification of different philosophical theories of well-being. This is important because patient’s well-being is often referred to in medical practice. However, the notion itself is unclear and contested. A common issue of contestation is whether well-being is subjective or objective. It will be argued that ontological and evaluative perspectives in this regard need to be disentangled. The ontological perspective is concerned with the problem whether well-being is a mode of consciousness or of existence. The evaluative perspective focuses on the criteria of well-being. There are then altogether four different accounts: (i) experience theories (ontological subjectivism), (ii) state-of-being theories (ontological objectivism), (iii) desire-fulfillment theories (evaluative subjectivism), and (iv) essence theories (evaluative objectivism). This classification is applied to a particular philosophical and social dispute, namely, whether and, if so, in what way disability undermines the quality of life of persons with disability.