Experiments are carried out in a paired packed-bed electrode reactor with the cathodic reduction of potassium ferricyanide coupled with the anodic oxidation of potassium ferrocyanide as the working system. Eight probes are used to determine the potential distribution. A two-dimensional model is developed and solved by the finite element method. Good agreement is observed between the experimental data and the model predictions for reactors of different sizes and operating conditions. The effect of the operating variables (cell voltage, electrolyte velocity, reactant inlet concentration and electrolyte conductivity) and the Sizes of the electrodes on the potential and concentration distributions are investigated by simulation.