Adsorption isotherms of hexafluoropropylene (HFP), methanol and ethanol were measured tinder dry and humid conditions using Norit RI carbon. The Presence of water lowered the HFP capacity over the whole pressure range as compared to the single component isotherm, while increasing the methanol and ethanol capacity. The Dubinin-Radushkevich equation was applicable for methanol, and ethanol, and the Dubinin-Astakhov equation gave a satisfactory description for water. The ideal adsorbed solution (IAS) theory satisfactorily described the binary, miscible systems of methanol and ethanol with water. Because water and HFP are not miscible, the IAS theory cannot be used. This binary system was described well by the independent co-adsorption of the two components, that is, HFP vapor is adsorbed in the micropore volume left free by water.