A semiclassical tunneling methodology has been adopted in order to comparatively analyze the tunneling splitting of malonaldehyde and hydrogenoxalate anion. This method proves to be very suitable to be applied to these systems. Analysis of the results allows a deeper understanding of the chemical difference of both systems. A clear dependence of the splitting on the ring size within which the intramolecular proton transfer takes place is found in agreement with our previous results. © 1992.