Surface water and groundwater is contaminated with pseudoperistent xenobiotics present in the environment. The risk associated with an increase in the consumption of drugs and their permanent occurrence especially in the aquatic environment falls on non-target organisms. The aim of this thesis was to assess the effect of increasing concentrations of paracetamol (0.1; 10; 100 mu g/l) on the growth and selected physiological parameters of the model organism Lemna minor (L.). Duckweed, as an important model plant for ecotoxicological research, has been subjected to a semichronic exposure to paracetamol. The presence of a stressor - paracetamol - after ten days of cultivation significantly influenced some growth and physiological parameters. It has been shown to significantly reduce the content of photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids), increase the value of non-photochemical quenching of chlorophyll fluorescence (NPQ), and lower the relative decline of chlorophyll fluorescence (Rfd). The results show that the increased load of paracetamol in the environment may negatively affect the growth of duckweed.