A pilot plant for electro-generation of hydrogen peroxide using an oxygen-reducing gas-diffusion electrode (GDE) was built and a mathematical model was developed to simulate the overall system. The electrode was made of a web coated with layers of VULCAN XC-72 Carbon catalyst on both sides of the assembly and a coating of SAB (Shawinigan Acetylene Black) on the gas-side. Electrolyses were carried out in galvanostatic mode. using catholyte consisting of 0.07 M NaCl solution, pH 2.7 and adopting a batch recycle mode of operation. Mathematical analysis was based on a three-phase model, and simulated the evolution of hydrogen peroxide concentration profiles in liquid-filled pores. Various models were developed to represent the behaviour of the cathode compartment in the electrochemical cell. The result is a tool which shows how hydrodynamics affect the performance of the overall system. Hydrogen peroxide production achieved during electrolysis can be calculated by means of this tool. Comparison of numerical simulations against experimental data validated the model developed in this study. (C) 2008 Elsevier Ltd. All rights reserved.