The N-2, H2O, and NH3 adsorption properties on hollandite-type (H-Hol) and birnessite-type (H-Bir) hydrous manganese oxides were compared with those on zeolitic crystals. It was found that the effective pore openings of H-Bir and H-Hol are below 0.3 nm. Although the geometric spaces on H-Bir and H-Hol available for physical adsorption from a gaseous phase are much smaller than those on zeolites, they can provide a strong chemisorption field for H2O and NH3 intercalation.