The contribution analyses the concept of life quality and ways of its assessing. In the foreground of the present mainstream assessment of life quality is the idea of measurement, from which the quantitative methodologies with particular measuring tools in different sciences (medicine,  psychology or economy) such as e.g. WHO QoL or Human Development Index introduced by the Organization of United Nations etc. derive. Through ontological analysis of the construction of life quality, the author arrives to single instruments in the so-called objectivist and subjectivist measurement of quality of life. The contribution concludes with reflections on the methodological problem of quality quantification and the need of an authentic measurement of quality of life.