IR spectroscopy of adsorbed probe molecules (CO, pyridine) is used to characterize the acidic properties of sulfated zirconia derived from zirconium oxide acid hydroxide. Their acidic properties are found to be similar. The strength of the Lewis and Bronsted sites measured by the frequency shift of adsorbed CO is lower than that in zeolites. It is concluded that sulfated zirconia have no superacid Bronsted and Lewis sites. Bronsted sites capable of protonating pyridine vanish when calcining the catalysts at temperature above 773 K, but the strength and concentration of the Lewis acid sites (LAS) do not change.