The effects of different cobalt precursor compounds on the structural and catalytic properties of cobalt metal and Co 3 O 4 catalysts have been investigated. The techniques employed for characterizing the different solids were XRD, ESR and TEM methods, together with their effectiveness as catalysts in the decomposition of H 2 O 2 at 30–50 °C. The results obtained indicate that the investigated catalysts contained clusters or very small particles of cobalt metal or Co 3 O 4 phases. Cobalt metal and Co 3 O 4 catalysts based on cobalt chloride exhibited higher catalytic activities than other catalysts derived from cobalt nitrate and sulphate salts, respectively, due to their decreased particle sizes. The activation energies of the catalytic reaction over the as-prepared catalysts revealed that the different precursor compounds did not modify the energetic nature of the active sites involved in the catalyzed reaction but changed their concentrations.