Alumina-supported manganese oxide catalysts as well as the parent formates were characterized my means of FTIR spectroscopy and nitrogen physisorption, Two different manganese formate solutions are used for the impregnation of alumina (4.8 and 8.0 mass%), The infrared bands in the high frequency region (OH stretches) indicate that the manganese complexes formed in the solutions are deposited gradually at the basic and acid surface OH groups. Part of the basic OH groups are neutralized with HCOOH (pH 5-5.2). The neutral OH groups remain unchanged during the impregnation. The nitrogen physisorption shows that the initial mesoporous character of the gamma-Al2O3 structure does not change during impregnation. The r(FHH) values which characterized the adsorbent-adsorbate interaction forces depend on the concentration of the impregnating solutions, i.e., on the type of the manganese complexes deposited on alumina surfaces. On the basis of the analysis of the pore size distribution curves the distribution of the supported formate and oxide phases is discussed,