The diffusion of platinum in thin copper films has been studied by Rutherford backscattering spectrometry (RBS) under the kinetic conditionsB(within the temperature range of 200–290 °C) andC(room temperature). The RBS spectra were modified to concentration curves for both bulk and grain boundary (GB) diffusion. Under the kinetic regimeBthe triple productsK&dgr;Db(Dbis the GB diffusion coefficient, &dgr; is the GB width,Kis the enrichment ratio) were obtained using Whipple’s model. Under the kinetic regimeCthe absolute value of the GB diffusion coefficient of Pt in Cu films was obtained. A comparison between the data on GB diffusion for the kineticsBextrapolated to room temperature and the data on GB diffusion for the kineticsCenables one to derive the productK&dgr; and to separate the contribution of segregation into the GB diffusion of Pt in Cu films. ©1995 American Institute of Physics.