The ionic diffusion rate and the electrochemically accessible surface area of the cathode, consisting of electrolytic manganese dioxide (EMD), were studied by means of ac impedance techniques. A simplified transmission line model was applied in the numerical fitting. The relationship between the pore size distribution and the ionic diffusion rate was investigated, as well as the pore size distribution and the cathode ‘spring-back’. EMD with a considerable volume of large pores was found to be beneficial not only for the high-rate discharge, but also for the cathode process during cell manufacture.