The optimization procedure of gas diffusion electrode (anode and cathode) development is described for a new type of low temperature fuel cell using as proton conducting electrolyte a concentrated aqueous solution of H3PW12O40 acid. The procedure consists of full factorial design of experiments performed by varying three variables : (a) content of polytetrafluoroethylene (PTFE) in the catalyst layer of electrodes; (b) content of fluoroethylenepropylene (FEP) in the diffusional (supporting) layer of electrodes; and (c) thickness of the diffusional layer of electrodes on three levels (low, medium and high) during the measurements of hydrogen permeability through dry electrodes, measurements of electrolyte absorption in the electrodes and during the electrochemical measurements of polarization curves for oxygen reduction, hydrogen oxidation and of the oxygen gain in a half-cell at room temperature. The results obtained demonstrate that the electrochemical activity in the half-cell reactions is regulated by the gas permeability of diffusional layer and wettability of the catalyst layer. The strongest influence on the observables has the polymer content in the diffusional layer. However, in the case of anode optimization, a strong interaction between the polymer content iii the catalytic layer and polymer content in the diffusional layer has been demonstrated.