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In order to get more insight into the characterization of nanoporous carbons by gas adsorption, the use of different probe molecules has been compared. A series of activated carbons with ranging porosity (burn-off) have been prepared from olive stones using CO₂ as activating agent and characterized using nitrogen and argon adsorption at low temperature (77.4K for N₂ and 87.3K for Ar) together with CO₂ adsorption at 273K and immersion calorimetry into liquids of different molecular dimensions. Experimental results show that argon adsorption in narrow carbon micropores takes place at a higher relative pressure compared to nitrogen due to a weaker effective adsorption potential (lower strength of dispersion forces), including the absence of specific interactions of argon with the adsorbent surface. We show further that application of advanced theoretical approaches based on the density functional theory …