Manganese oxides supported on ordered mesoporous silicas and nonordered commercial silicas were comparatively studied in terms of physical properties and catalytic behavior in the complete oxidation of propane, n-decane, toluene, and p-cymene. Manganese oxides are well-dispersed on large-pore SBA-15, KIT-6, and commercial silicas, whereas they agglomerate on small-pore HMS and MCM-41. Mn/SBA-15 contains oxide species with the best reducibility, but its two-dimensional mesopores are significantly blocked. The alkane removal efficiency depends on the amount of accessible manganese oxides; therefore, the three-dimensional Mn/KIT-6 shows better performance than the pore-blocked Mn/SBA-15. In contrast, the ignition of aromatic hydrocarbons, which needs higher temperatures than alkanes, seems more strongly dependent on the reducibility, and Mn/SBA-15 shows the lowest ignition temperatures. Despite their much smaller surface areas, nonordered commercial silicas present significant advantages in the catalytic removal of large-molecule hydrocarbons due to the favorable mass transfer in the short mesopores within their thin particles.