Based on the series of benzene adsorption and related enthalpy of adsorption data measured on porous carbons that possess various porous structures, we show that the creation of a solidlike structure in pores depends on the average pore diameter of an adsorbent. Taking into account the solidlike adsorbed phase in the thermodynamic description of the adsorption process via the formalism of the theory of volume filling, of micropores (TVFM) leads to very good agreement between the data measured experimentally and those calculated from TVFM. Finally we show that the boundary between solidiike and liquidlike structures of benzene molecules in carbon pores is located around the average pore diameter., close to ca. 2.1-2.4 nm. (c) 2005 Elsevier Inc. All rights reserved.