Two samples of activated carbon of wood origin were oxidized using ammonium persulfate. The samples were characterized using sorption of nitrogen and Boehm titration. Then, the adsorption of diethyl ether was studied on the initial samples and their oxidized counterparts by means of inverse gas chromatography at finite concentration. Adsorption isotherms were obtained from the chromatographic peaks using a characteristic-peak elution method. Then, the isotherms at temperatures between 393 and 433 K were used to calculate the isosteric heats of adsorption. The results showed a difference in the uptake of diethyl ether depending on the porosity of the sample and its surface chemistry. Analysis of the heats of adsorption revealed that the diethyl ether molecules are adsorbed on the carbon surface via two different adsorption mechanisms. First, hydrogen bonding to functional groups in narrow pores significantly contributes to the adsorption. Second, pore sizes govern the adsorption uptake as a result of interactions of the hydrocarbon moiety with the pore walls.