FT-IR spectra of the co-adsorption of benzene and CO have been performed to identify the preferred adsorption sites of hydrogen and benzene on a Pt/SiO2 catalyst for hydrogenation of benzene. Results of CO adsorbed on atop sites on Pt/SiO2 includes: an alpha peak at 2091 cm(-1), a beta peak at 2080 cm(-1) and a gamma peak at 2067 cm(-1) indicating three kinds of adsorption sites for dissociative hydrogen on Pt/SiO2. The site of lowest CO stretching frequency offers stronger adsorbates-metal interaction for benzene and hydrogen. Hydrogen binding on the site of lowest CO stretching frequency before benzene adsorption significantly enhances the reaction rate of benzene hydrogenation.