Abstract Small Pd and Au clusters were grown on carbon by metal vapor deposition under UHV conditions. The cluster growth was followed by XPS. Changes of lineshape and binding energy of core level peaks were followed in a wide range of cluster sizes. Analysis of the results showed that core levels from well-defined particles exhibit a quasi-symmetrical shape in agreement with change of relaxation energy induced by size effects. Gold core levels showed evidence of this interpretation as their asymmetry could be explained by size dispersion of gold clusters only. We followed also the change of the intensity ratio of two photoemission peaks of the deposited metal versus the cluster size. This method could be easily applied for size evaluation to various supports or even powders.