In this research the toxic effects of Cd accumulation on Quercus robur ssp. robur L. (common oak) and Acer negundo L. (box elder) were investigated. Tree seedlings, grown in hydroponic cultures for 4 months, were exposed to different Cd concentrations (3, 9, 27, 81 muM) for 16 days. Cd concentrations in plant organs, total chlorophyll content and peroxidase activity were detected. Cd accumulation in plants increased with increasing concentrations of this heavy metal in the growth medium. Cd was mostly accumulated in the roots, followed by the shoots and leaves, respectively. Decrease in chlorophyll content and fluctuations in peroxidase activity were determined (P <0.05). Among the investigated tree species, Acer was found to be more tolerant to Cd pollution in comparison to Quercus. We suppose that Acer can be planted in the polluted urban areas including urban-parks and roadsides.