Do cities have an optimal size? In seeking to answer this question, various theories, including Optimal City Size Theory, the supply-oriented dynamic approach and the city network paradigm, have been forwarded that considered a city's population size as a determinant of location costs and benefits. However, the generalised growth in wealth that has been experienced over the last 50 years in developed countries has changed what have traditionally been seen as man's needs. Thus, Inglehart's post-materialist approach and Maslow's theory of human needs force us to re-examine the traditional costs and benefits of cities. Here, we assume that costs and benefits enter the utility function of households through the quality of life concept. The relation between the constituents of quality of life and traditional and new theories of city size are considered here. Finally, we test these relations empirically in a specific dynamic, local framework: the city of Barcelona (Spain) in the period 1991-2000.