The adsorption isotherms of caffeine from aqueous solution onto three hydrogen donating adsorbents - hydroxypolystyrene. polystyrene-azo-pyrogallol, and D72 resin-were measured. The adsorption enthalpies calculated from the isotherms according to the Clausius-Clapeyron equation were-24~ -36kJ/mol, -32~ -37kJ/mol. and -19~ -24kJ/mol respectively These values implied that the absorption processes were based on hydrogen bonding. Furthermore, the mechanism of the adsorption of caffeine onto D72 resin was studied by IR spectra and the small molecular model experiments. and the results showed that the adsorption of caffeine onto hydrogen donating adsorbents was based on hydrogen bonding. The adsorption isotherms of caffeine from aqueous solution onto three hydrogen donating adsorbents - hydroxypolystyrene. Polystyrene-azo-pyrogallol, and D72 resin-were measured. The adsorption enthalpies calculated from the isotherms according to the Clausius-Clapeyron equation were -24 ~ -36 kJ / These mechanisms imply that the absorption processes were based on hydrogen bonding. Also, the mechanism of the adsorption of caffeine onto D72 resin was studied by IR spectra and the small molecular model experiments. and the results showed that the adsorption of caffeine onto hydrogen donating adsorbents was based on hydrogen bonding.