The article presents the population problem of urban functional area around chosen mediumsized cities in Poland and Czech Republic. The research concentrates on 6 cities (on the Polish side – Jelenia Góra, Legnica and Wałbrzych – located in Lower Silesia region; on the Czech side – Hradec Králové, Liberec and Ústí nad Labem). These core cities with suburban areas co-create the functional urban areas with
a varied demographic structure and development dynamics. In the analyzed period, the population growth was observed only in Liberec. The largest total population among the studied areas refers also to Liberec functional urban area. The population in the suburban areas on the examined Polish and Czech cities are relatively younger than in the core cities. The functional approach to the development of urban areas, which assumes departing from the perception of problem and challenges only through the prism of administrative borders is becoming more and more important.