After a short historian concerning the development of the subtle sets theory, we specify the conventions related to the notation used in this paper and we define the concept of sequence. Several versions of defining the subtle sets and several forms of representing the subtle space are used. At the same time, the hypotheses laying at the basis of using the subtle sets theory in order to study the quality of life, are presen-ted. Seven stages have been delimita-ted, which had been experimentally applied to a comparing study of life quality in Bucharest, between a family living in the central area and a family living in suburbs. Nine criteria have been selected, in order to define the family’s condition living in the central area, respectively, in suburbs. The conditions of the observed family were analyzed by using certain epithets or by numerical measurements which have been converted into membership degrees, according to the fuzzy sets theory. An aggregated membership degree of life quality, µg, and another antithetical one of non-quality, µg were given for each central area, res-pectively, suburbs. This fact allowed to calculating the discrepancy µg – µg The managers working in public adminis-tration have to reduce the size of this discrepancy.