Benzene and its substituted analogs are considered hazardous because of their high risk to public health and the environment. Porous carbon materials are widely studied for their potential ability to act as a filter of carcinogenic materials. This study uses first-principles calculations to explore the selective adsorption of benzene and benzenes with substituents varying in electronegativity and size in a graphitic slit and (9,9) carbon nanotubes. The results show that the molecular adhesion energies are dependent on the bulkiness of substituent but are much less dependent on their electronegatives. (C) 2004 Elsevier B.V. All rights reserved.