In order to conceptually define quality of life (QOL) in dementia, the literature on QOL in the elderly population, in chronic disease and in dementia was studied. Dementia is a progressive, age-related, chronic condition and to avoid omissions within the dementia-specific concept of QOL, a broad orientation was the preferred approach in this literature study. Adaptation is a major outcome in studies investigating interventions aimed at improving QOL in chronic conditions, but to date, it has not been used in the definition of QOL. It is argued that adaptation is an important indication of QOL in people with chronic diseases and therefore also in dementia. Some crucial issues in assessing dementia-related QOL that are relevant to clarify the continuing debate on whether QOL, particularly in dementia, can be measured at all, are discussed. Then the following conceptual definition is offered: dementia-specific QOL is the multidimensional evaluation of the person–environment system of the individual, in terms of adaptation to the perceived consequences of the dementia.