The article deals with international coordination of social security in the EU, aiming special focus on self-employed persons. The article outlines an overview of international social security coordination system with its legal sources and presents original research using cluster analysis method based on statistical data compiled by European Commission experts. The presented research is based on a conducted cluster analysis bringing together principal macroeconomic characteristics describing relative size and relative strength of economies, in particular total number of inhabitants, GDP per capita, in internationally comparable purchasing power parity version, and average wage, with quantitative expression of labour migration, represented by short term mobility covered by the European law posting provisions. The research question was formulated towards exploration whether there are some common features in short-term mobility inflows created by independent self-employed persons in the European internal market. The results showed prevailing lack of consistency leading to the fact that the clusters reported by the model were not comparable in size, when two of them embraced nearly all the examined European countries and the other two only few of them.