Cities function in people's minds as reservoirs of opportunities and possibilities. For many people, living in a city seems an attractive and logical life choice compared to areas perceived as provincial. However, the reality of the modern city is also associated with numerous nuisances. The occurrence of these disadvantages has led to the development of mechanisms intended, at least in principle, to counteract the ills of urban life. One such mechanism is the phenomenon of suburbanization. The outpouring of urban functions beyond its boundaries occurs all over the world. However, this phenomenon also entails exacerbating transport bottlenecks, requires a lot of local investment, contributes to the deterioration of the environment, and disrupts household time budgets. This paper addresses population change as one of the demographic aspects of suburbanization. The trends characterizing the outflow of population from cities and the inflow of population to suburban areas has been examined. The study covers several of Poland's largest cities using data from the 2011 and 2021 National Censuses. The main objectives of this study are to assess the scale of suburbanization in large and medium-sized Polish cities, so as to determine whether suburbanization occurs similarly regardless of city size. To identify those urban centers where the population change in neighboring municipalities is particularly high so as to raise the awareness of decision-makers and real estate market participants in relation to the challenges posed by suburbanization. In addition, using one city as an example, an assessment of how the influx of population affects number of transactions on selected real estate market was carried out. The results of the study may be useful in analyzing investment needs for various types of infrastructure, including roads and technical infrastructure.