A process for depolymerizing and/or chemically modifying lignin or lignin-like compounds in which a solution of copper and peroxide acts on lignin and/or lignin-like substance at a temperature of less than 100° C., characterized in that the solution is an aqueous solution containing copper or a copper complex, a coordination compound and peroxide and wherein the concentration of the copper or copper complex is between 0.001% and 5%, and wherein the concentration of the coordination compound is lower than 20% and wherein the concentration of peroxide is between 0.01% and 20%.