The Cu, Pb and Zn adsorption capacity of two municipal solid waste composts was studied in batch experiments where the equilibrium isotherms were determined. Both composts, despite having very different metal concentrations, showed high sorption capacities for the three elements, with the following affinity sequence: Pb > Cu > Zn. The maximum sorption capacities of the composts, on the basis of the Langmuir isotherm, were roughly equivalent to 1 mmol g(-1) for Pb, 1/2 mmol g(-1) for Cu, and 1/3 mmol g(-1) for Zn, which makes of both composts good biosorbents. Although a slightly higher adsorption capacity was seen for the compost with the lowest previous metal content, this fact alone could not explain the difference in the performance of the composts, and other factors such as its higher organic matter concentration and higher cation exchange capacity could have been more determinant. (C) 2011 Elsevier Ltd. All rights reserved.