In the paper the author attempts to carry out a comparison between the floristic composition and structure of plant communities present in cereal crops of the rural areas of the Siedlce Upland and the floristic composition and structure of the analogue plant communities found in the area of Siedlce, which is the biggest town of this geographic mesoregion. Tables of the following syntaxons were analysed in the comparative analysis: Papaveretum argemones, Papaver argemones-Vicia tetrasperma, Vicietum tetraspermae scleranthetosum and Vicietum teraspermae typicum. It was observed that the urban plant communities had a greater floristic variety, a greater participation of perennial and ruderal species, as well as, a more complex phytosociological structure, with the exception of few typical patches, comprising diagnostic species of various syntaxons.