This paper presents the changes in urban population density in the twentieth and twenty-first centuries in an area of approximately 20,000 km2 in southern Poland, which includes close to 100 towns and cities with a population of almost 4.5 million (in 2011) and an urbanisation index over 70%. It is the most urbanised part of Poland and includes the Cracow agglomeration and the Upper Silesian conurbation. The analysis was performed using one of the statistical methods for estimating discrete distributions, the