The book presents results of the project “Reduction of Negative Impact of Alien Invasive Plant Species on Ecosystems and Human Wellbeing in Cross-border Region of Lithuania-Belarus (ENI-LLB-1-207, Alien Invasive Plants)”. During the implementation of the project, eight invasive plant species were inventoried and mapped in the transboundary region of Belarus and Lithuania according to the common methodology. The following invasive species were selected for the evaluation: Acer negundo, Asclepias syriaca, Echinocystis lobata, Heracleum sosnowskyi, Solidago canadensis and Solidago gigantea. Acer negundo was the most frequent in the target area. It prevailed both in terms of the number of occupied sites (69% and 44% of all sites invaded by the study species in Lithuania and Belarus, respectively) and in terms of occupied area (5.5 thousand ha and 0.8 thousand ha in Lithuania and Belarus, respectively). Echinocystis lobata and Solidago canadensis are also widespread invasive species in the territory. However, Solidago canadensis was more frequent in Belarus, whereas Echinocystis lobata was much more widespread in Lithuania. The frequency of Impatiens glandulifera is just slightly higher in Lithuania than in Belarus. It should be noted that the most dangerous invasive species, Heracleum sosnowskyi, was quite rare in the project target area.