This diploma work is focused on evaluation of occurrence and spread of selected botanical communities of invasive species in cadastral area of city Veľký Krtíš and its surroundings. The intention of work is to develop floristic, phytocoenological and ecological description of communities of invasive species. All data were obtained during a field research in investigated area. We have registered 40 phytocoenological reports during growing period from June until the end of September in 2016 with respect to principles of the Zürich-Montpellier school (Braun-Blanquet, 1964). The records were subsequently processed by Turboveg and Juice software. We have detected 6 dominant types of communities: community with Aster novi-belgii, with Impatiens parviflora, with Fallopia japonica, with Solidago canadensis, with Solidago gigantea and with Stenactis annua. Vegetations are predominantly poor in species, mostly dominated by one invasive species. Vegetations are often observed on small areas in their initial phase. Vegetation with Stenactis annua is most widespread in this area, recorded on 10 sites with 76 species. The least widespread vegetation is with Aster novi-belgii, found on 4 sites with 26 species. Besides herb layer we have recorded species in bushes and tree layers on some sites, too.