A mathematical model to represent three-dimensional bipolar electrodes is proposed taken into account the leakage current. The model is analytically solved when the electrochemical reaction has a mass-transfer control at low overpotentials, which represents a limiting case of the general mathematical treatment. For this simplified situation, expressions are deduced to evaluate the current and potential distribution and to calculate the leakage current. The effect on the leakage current of kinetic, electrochemical and geometric variables, which are lumped into one dimensionless number, is discussed. The influence of the leakage current on the optimal bed depth under limiting current conditions is also analyzed. Likewise, experimental data, using the deposition-dissolution of copper as test reaction, are compared with the theoretical prediction of the general treatment achieving a good agreement between both.