The data are presented for Ni selfdiffusion and Au heterodiffusion in nanocrystalline Ni. Volume diffusion coefficients are much greater than those for a coarse – grained polycrystals extrapolated from high temperatures. Interface diffusion parameters were calculated based on the assumption that B – kinetic regime is realized at temperature range more than 448 K, while C – kinetic regime is realised at temperatures less than 423 K. The consistency of obtained results with the proposed cluster diffusion model is discussed. Diffusion in Au – Cu thin films (from several tens to several hundreds nanometers) was studied with the use of the Rutherford Back Scattering, RBS, under the kinetic regime B (448 – 523 K). The RBS spectra were transformed in the concentration depth profiles for both volume and grain boundary (GB) diffusion. The triple products Pn = snδDn (sn is the enrichment coefficient, while δ is the nanograin boundary width) were calculated using Whipple model. As a result of this analysis the s – value for Cu – Au system was determined to be of the order of unity. The paper is focused on a difference between GB diffusion parameters in nano – and coarse grained materials.