Attractive public spaces are among the magnets encouraging people to settle down in. In this context, a question ought to be posed: how should public spaces be planned along with the phenomena of depopulation occurring in cities? The cognitive goal is to determine the relationship between urban shrinkage manifestations and public space planning on the example of selected Polish cities with more than 500,000 inhabitants. The practical goal is to set recommendations for the adaptation of urban spatial development policy in response to contemporary threats. Cultural, national or economic factors are less and less affecting the formation of territorial ties. Due to the increase in mobility, the population flow also increases. On the one hand, the phenomena of migration affect urbanization processes, but on the other hand, the quality of the urban environment has also impact on whether the number of inhabitants will increase or decrease. Cities that do not conduct proper spatial development policy will be subject to the phenomenon of depopulation. In Poland, more than half of large centers have shrunk over the last twenty years. Based on urban development research, we can distinguish the following stages: urbanization, suburbanisation and deurbanization. What is paradoxical, is that the foundation of these phenomena are activities colloquially considered as factors of development: the development of road infrastructure, increased mobility, good conditions for construction in the suburbs. The outflow of inhabitants will systematically increase, as long as the spatial development policy does not improve. Without taking a decisive action, this problem will deepen and may result in social destabilization, economic decline and, ultimately, the collapse of the city. Deurbanization processes, which take place in shrinking agglomerations, impact the worsening of land use, the increase in the costs of urban infrastructure functioning and the diminishing in population density of central districts or inner-city areas. In many of the cities that have been examined, it is necessary to carry out spatial optimization. The current policy based on area growth ought to be oriented towards qualitative growth. The work addresses the problems of depopulation in Polish cities and describes their scale and scope of influence on the shaping of urban structures. The ways of planning public spaces with demographic conditions in the background have been presented. Based on the experience of cities introducing strategies of smart urban shrinkage, basic solutions have been outlined along with the possibilities of their application in conditions regarding the Polish cities. [ABSTRACT FROM AUTHOR]