This article raises the issue of changes in the structure of use of agricultural land in Poland and the Czech Republic since the accession of both countries into the structures of the European Union. An important question raised in this article is the analysis of changes in the area structure of agricultural holdings according to adopted agricultural land groups. The analyses were based on the graphic method of analysing concentration strength – the Lorenz curve to determine the distribution of the number and surface area of agricultural farms in the given area groups and the percentage share of such farms in these area groups. Additionally, the Gini coefficient was calculated for the same phenomena, to measure the concentration (inequality) of the random variable distribution. The research has shown the structural change trends in the agricultural area of analysed countries as well as varied structural situation of agricultural holdings during the accession period. The condition translates into a slower pace of structural change of agricultural holdings in Poland and a faster process of enlarging the area of agricultural holdings in the Czech Republic.