Studies which deal with the reasons for disparities between the levels of regional development are an important part of economics theory. According to the neoclassical approach, all differences are transient and they will gradually diminish, owing to various factors, including perfect mobility of the means of production. On the other hand, according to the theories from New Economic Geography, regional polarisation of economic development is a relatively permanent process and the mechanism of its increase is based on so called agglomeration benefits. Based on this concept, the study assumed that one of the basic reasons for the disparities between the levels of economic development is the diversity of the development of an urban settlement network. In order to verify the hypothesis, sixteen provinces were divided into three groups with different levels of economic development, measured by the value of GDP per capita. Subsequently, the development of urban settlement network was evaluated within such groups by means of such indexes as: urbanisation index, city density index, structure of urban centre by size. The analyses performed have confirmed the assumption. At least partially, economic development of provinces depends on urbanisation processes. However, it means that development disparities between regions are likely to grow in the future.