The kinetics of the photoeffect in the system lithium/surface passivating film/non-aqueous electrolyte solution was studied using the laser pulse method. A theoretical analysis was performed of electron photoemission kinetics from the metal into an ion-conducting passivating film which, in particular, may have traps. Comparison of experimental and calculated curves showed that the decreasing part of the oscillograms (current-time curves) could be described by the equation of non-stationary diffusion for concentration of photoemitted electrons, This macroscopic diffusional motion in disordered solids can arise from microscopic random trapping and detrapping events and the corresponding diffusion coefficients must be considered as effective ones. The values of effective diffusion coefficients of electrons in passivating films formed at the lithium surface in a 1 M solution of LiClO4, in a mixture of propylene carbonate with dimethoxyethane were determined and were equal to ca. 10(-14) m(2) s(-1) at 298 K.