The utilization of bottom ashes from municipal solid waste incineration (MSWI) in road constructions might cause environmental problems due to the release of toxic metals. The present work is aimed at studying the suitability of soil as a treatment facility of metals leached out from bottom ashes. A laboratory experiment with three types of soil (forest soil, peat and mould soil), and with sand as a reference substrate, was performed to determine the binding capacity of each substrate towards heavy metals, such as Cu and Cr(VI). The results indicated that all the substrates were capable of removing on average 99,3 % of Cu from the solution, while only peat showed a high retention of Cr(VI) (96,2 %). The retention of Cr(VI) was directly proportional to the soil organic matter (SOM) content, while the retention of Cu had no correlation with the SOM of the substrates. A high retention of Cu shown by sand was due to its high content of pH which could favor the precipitation of Cu(OH)2. A synergetic effect of Cu on the retention of Cr(VI) by sand and mould was detected, i.e. increasing concentrations of Cu in the solution increased the retention of Cr. In all the other cases there was no statistically significant interaction between the retention of Cu and Cr(VI) by the analysed substrates.