Currently, the demographic ageing of the population is becoming relevant for Belarus, Kazakhstan and Russia. The present research analyses the process of population ageing. The hypothesis of the study was to identify the unidirectional nature of the processes of demographic ageing in different economic and social conditions. The research methodology includes the spatial and temporal assessment of population ageing based on the data of the national statistical services of the countries for 2014-2020. Particular attention is paid to the analysis of population ageing indicators: indicators of demographic population ageing, indicators of the causes of population ageing, indicators of the consequences of population ageing. The conducted research demonstrated an increase in demographic population ageing in Belarus, Kazakhstan and Russia. Based on the analysis of population ageing indicators, the differences in the intensity and causes of the ageing process in the countries are revealed.