A planar polarographic probe for determining the lambda value of gas mixtures, in particular exhaust gas of internal combustion engines, is disclosed, as well as a process for producing the same. The planar polarographic probe has a pumping cell A with outer and inner pumping electrodes (11 and 16) arranged on a solid electrolyte (14). The gas to be measured can be supplied to the inner pumping electrode (16) through a diffusion barrier. The probe further has one front and two lateral frontal surfaces. The diffusion barrier is designed as a diffusion layer (19) which at least partially covers the inner pumping electrode (16) and which is exposed to the gas to be measured at at least one frontal surface of the probe. To produce the planar polarographic probe one uses a multiple printed panel, on which the diffusion layer (19) is applied in such a way that the diffusion layer (19) overlaps at least the front edge of the multiple printed panel and when the individual printed panels are singled out, the diffusion layer is exposed.