Purpose. To investigate special aspects of accumulation of inorganic elements including heavy metals in seeds of white and black mustard to be grown for obtaining drugs. Methods. Field experiments, microwave digestion, ICP-MS and statistical analysis. Results. The content of inorganic elements including heavy metals was determined in the seeds of white and black mustard grown in Kiev Oblast. It was revealed that during the growing season plants of white mustard were able to accumulate such elements as aluminum, barium, strontium, zinc in seeds in concentrations that exceed their content in black mustard seeds, while compounds of calcium, cesium, iron, magnesium, manganese, potassium in a greater degree were accumulated in black mustard seeds. Conclusions. As legal and regulatory documents for important chemical elements don’t contain the maximum permissible limits of their content in medicinal plants, it would make sense to launch a comprehensive research with the involvement of specia­lists of relevant profiles in order to establish such a gradation. Plants of white and black mustard in Kiev Oblast have accumulated high levels of such metals as Ba, Cu, Fe, Mn, Mo, Sr, Zn that exceed the known limits of accumulation, indicating a partial contamination of soils in the region. Consequently, these plants can be used for phytoremediation of soils. Considering the fact that in the pharmaceutical practice refined mustard seed oil is used, revealed alterations of metal accumulation in seeds will not affect the quality of the final drugs. According to the research results, white and black mustard is promising for cultivation in Kiev Oblast with a view to obtain raw material that can be processed into drugs.