A comparative study of pristine and thermally treated (medium-temperature reduction, MTR, 573 K, 1 h) Pd-graphimet was carried out to establish the changes arising in structure and catalytic activity. The structural investigation was performed by means of BET surface area analysis, transmission electron microscopy, small-angle X-ray scattering and H-2 titration. In order to distinguish between the hydrogenation and isomerization sites of the samples, the single turnover reaction of l-butene was applied. For pristine Pd-graphimet, the experimental evidence confirmed the presence of interlayer metal and surface metal particles of different sizes. Although the catalytic activity was clearly attributable to the 1-2 nm surface Pd crystallites, the interlayer metal content also had an influence on the reaction through deintercalation which first started at 323 K. Nevertheless, the effect of MTR was found to be far more pronounced : all the inserted Pd atoms underwent migration and a moderate sintering of the surface Pd crystallites took place. Data on the transformation of l-butene indicated that Pd-graphimet was similar in effect to supported Pd catalysts.