Paired reactions on interdigitated anode/cathode were studied by finite element simulations and compared to those occurring in classical parallel plate electrochemical cells. The results clearly show that coplanar interdigitated electrode systems provide an advantageous geometry for paired reactions between two products electrochemically generated on both anode and cathode. The influence of the reaction rate constant, the inter-electrode gap and the flow rate. on the concentration profile and on the conversion rate is investigated. Due to the alignment of the electrodes on the same flow line, diffusion layer overlapping is more easily obtained with this geometry. (C) 1998 Elsevier Science Ltd. All rights reserved.