An application of time-of-flight secondary ion mass spectrometry (TOF-SIMS) to the surface investigations of Co/Al2O3 catalyst is presented. The chemical composition of catalyst surface was determined. Moreover, the presence of interactions between metal oxide and support was confirmed. Owing to the calculation of CoO2+/CoO+, CoO3+, /CoO+ and CoO3+/CoO2+ intensity ratios the estimation of cobalt reduction degree was possible. A considerable part of this work was devoted to the investigations of metal distribution on the catalyst surface. TOF-SIMS surface images gave evidence of the cobalt dispersion improvement after sample reduction.