Himalayan balsam is an annual plant from the balsam family, originating from the Himalayan part of Asia. It's been present in Europe since the XIX century and it has become one of the most recognizable invasive plants. It is found also in Slovenia, mostly in riparian zones and ruderal areas. In this thesis, we present the state of its populations in Nature park Ljubljansko barje from the year 2019. Mapping was based on data from the previous season, in aim of determining whether it has been spreading on the discussed area in one year. Although several authors often provide data of its fast spread by waters, we could not confirm that. Only few of the newly established populations were found, while the short distance local spreading nearby the parent plants was confirmed. Our results didn't point out the importance of Ljubljansko barje's water bodies in species' spreading. The results of accompanying flora's inventarization have confirmed the species' preference for moist and fertile habitats, although it was able to survive in ecological conditions somewhat different, surrounded by generalists and other allochthonous species. Due to those results, we assume that, without the proper management, distribution of the Himalayan balsam in Slovenia will expand in many of country's parts, except for the higher mountains and warmer parts of the Sub – Mediterranean region.