Using the technique of gaschromatography the zero adsorption heats Q(0) were determined on activated carbon for 11 halogenated hydrocarbons (FCC＇s and perfluorinated n-paraffins) and the corresponding n-alkanes with the same number of C-atoms. The total substitution of H- by F-atoms in the n-paraffins results in an increase of the Q(0) values as well as a consecutive substitution of F- by Cl-atoms in CF4. Large differences were found comparing the zero heats of adsorption of the adsorptives investigated on activated carbon with Q(0) data measured on a DY zeolite. The carbon adsorbent exhibits zero adsorption heats which are up to 100% higher than those of the DY zeolite. Simple equations are presented for the dependence of the Q(0) values on physico chemical constants of the adsorptives.