Carbon aerogels (CA), having well-defined pore structure and different surface chemistry natures, were used to study the adsorption of supercritical N-2 and O-2 at 303 K. alpha (s), Langmuir, and DR methods were applied for interpretation of the experimental adsorption data. The surface chemistries were analyzed by XPS, The effect of the pore width and the surface chemistry on the supercritical gas adsorption is discussed. Ce, Zr-doped CA adsorbs more supercritical N-2 and O-2 than CA. This effect is unlikely to be due to the pore structure, since Ce, Zr-doped CA has wider micropores. The larger contribution of specific interactions between substrate sites and the adsorbate at ambient temperature appears to play a very significant role.