The effect of preparation and calcination on reducibility, dispersion and catalyst activity of Co/SiO2 catalysts was studied. The Co/SiO2 catalysts were prepared by a gas-phase deposition technique, atomic layer epitaxy (ALE), using Co(acac)(3) as precursor and by impregnation from Co(NO3)(2). The cobalt content of the catalysts varied from 5 to 20 wt.%. The cobalt loading of the ALE catalysts was increased by repeating Co(acac)(3) and air reaction sequences. Air calcination of ALE catalysts (＇calcined＇ catalysts) produced cobalt species at least partly in the form of silicates that were hard to reduce. The reducibility was enhanced when the calcination step after the last Co(acac)(3) reaction step was omitted (＇uncalcined＇ catalysts). This could be explained by a more easily reducible layer on the surface of the catalysts containing ligand residues from the precursor High reduction temperatures were still needed compared to the impregnated catalysts. However, the cobalt dispersion on the uncalcined ALE catalysts was in the same range as on the calcined catalysts and clearly higher than on the impregnated catalysts. The uncalcined ALE catalysts showed significantly improved activities in toluene hydrogenation compared to the calcined ALE and the impregnated catalyst.