The scope of this work was to control the pore sizes of porous carbons by various surface treatments and to investigate the relation between pore structures and hydrogen adsorption capacity. The effects of various surface treatments (i.e., gas-phase ozone, anodic oxidation, fluorination, and oxygen plasma) on the micropore structures of porous carbons were investigated by N-2/77 K isothermal adsorption. The hydrogen adsorption capacity was measured by H-2 isothermal adsorption at 77 K. In the result, the specific surface area and micropore volume of all of the treated samples were slightly decreased due to the micropore filling or pore collapsing behaviors. It was also found that in F-2-treated carbons the center of the pore size distribution was shifted to left side, meaning that the average size of the micropores decreased. The F-2- and plasma-treated samples showed higher hydrogen storage capacities than did the other samples, the F-2-treated one being the best, indicating that the micropore size of the porous carbons played a key role in the hydrogen adsorption at 77 K. (c) 2007 Elsevier Inc. All rights reserved.