Aquatic ecosystems are a valuable part of natural environment. The increasing level of pollution in waters transforming biocoenoses and other adverse effects of the impact of toxic substances have contributed to the development of biological monitoring. The aim of the study was to determine the changes in contents of zinc and lead in bottom sediments and roots of aquatic plants: Phragmites australis and Acorus calamus in the river Narew. There were 14 points on the river, from where samples of bottom sediments and plant material were collected. The contents of lead and zinc were determined by means of flame atomic absorption spectrophotometry using Varian device. It was proven that bottom sediments were characterized by low contents of zinc and lead except from two sampling points: in Bondary and Narew. Achieved results of analyzes of plant material showed a slight exceeding in the case of lead. Spatial distribution of zinc and lead contents in examined roots of plants coincided with their contents in bottom sediments, which was also confirmed by statistical analysis. It was proven that aquatic plants had greater tendency for accumulation of metals than bottom sediments.