In Poland the energy sector is 80% based on coal and lignite, therefore the problems associated with air pollution by fuel combustion by-products are of great importance. Carbon and sulphur dioxides, polycyclic aromatic hydrocarbons, dioxins, furans and heavy metals such as cadmium and mercury have a significant effect on ambient air quality, influencing human health and the state of ecosystems. The aim of the research was to evaluate the effect of two coal-fired power plants in Warsaw on vegetation in their vicinity. Achillea millefolium was selected as a representative bioindicating species, because of its high phytosociological constancy in the two power plant areas and its relatively high c-DNA value. Morphological and cytogenetic changes were observed, indicating the adverse effect of a power plant on the vegetation in its central area and close vicinity, potentially leading to gradual degradation and adverse landscape changes.