The influence of the interfaces on the diffusion in Pd films of Pd-Ag and Pd-Au polycrystalline systems at a temperature near 500 K was studied. An X-ray diffraction technique based on the analysis of the profile change of line (111) in the diffusion zone was used. The decrement of the diffusion coefficient in Pd film under transition from Pd-Ag-glass and Pd-Au-glass structure to Ag-Pd-glass and Au-Pd-glass structure was established. This result is explained by the influence of interphase surfaces on the mobility of dislocations along which the diffusion happens.