The article presents the results of research into the standards of living in Poland and old European Union member states in 1990-2000. The research was conducted on the basis of select taxonomic methods. The analysis of the empirical material was designed to determine whether or not the standard-of-living gap between Poland and the EU-15 narrowed over the decade. An additional aim of the research was to confirm the positive effects of integration following an improvement of population living standards and shrinking differences among individual member states. The author characterizes taxonomic methods with a special focus on those used in the research. He also discusses the results of the analyses conducted. The comparison of Poland and the EU-15 was made on the basis of criteria of similarity and discrepancy, while the Ward method was used to identify groups of countries characterized by a similar standard of living in 1990 and 2000. The analysis of the empirical material reveals that in the period covered by the research-despite the consistent growth of population living standards-Poland did not bridge the gap separating it from the EU-15. In fact, the gap widened. However, population living standards continue to improve and differences among individual EU countries are shrinking as integration progresses.