Salix americana willow bark is a waste arising in the process of wicker decortication that so far has not found any practical application. The bark can adsorb metal ions, because in its composition among others are phenolic groups which may be involved in the removal of metal ions from water solutions. The results of sorption of copper(II) and zinc(II) on modified willow bark of Salix americana were presented. The bark was modified with nitric and sulfuric acids at concentrations ranging from 5 to 15%. The best adsorption results were obtained using 15% nitric acid for modification. Adsorption of metal ions from aqueous solutions at concentrations raging from 20 to 100 mg/dm3 was studied. It was found that an increase in the initial concentration of copper(II) and zinc(II) resulted in an increase in their adsorption on the modified cortex.