Palladium catalysts promoted with a second metal demonstrate good activity and selectivity in many important oxidation and reduction reactions. The influence of co-metal on the catalytic performance of Pd depends on interaction between the two components and by the chemical state of both the Pd and co-metal. The understanding of the nature of such interaction is important in the optimization of such catalysts and development of new Pd-based catalyst systems with improved performance and stability. In this study, the surface structure and chemical states in several Pd-M/supported catalysts (where M = In, Bi, and Te) were experimentally investigated by using time-of-flight secondary ion mass spectroscopy (ToF-SIMS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It has been found that the formation of the intermetallic compounds and their composition can be responsible for a reduction or increase of catalytic activity and selectivity previously observed for the studied Pd-M systems. (C) 2013 Elsevier B. V. All rights reserved.