Adsorption of low concentration formaldehyde on pitch-based, rayon-based, and PAN-based activated carbon fibers (ACFs) and an unactivated PAN-based carbon fiber (PAN-CF) was investigated by a dynarnic method. The pore structure and surface chemistry of these samples were characterized by liquid nitrogen adsorption, elemental analysis, and X-ray photoelectron spectroscopy. Results revealed s that the pore structure, especially surface chen-dcal composition, greatly influence the formaldehyde adsorption. PAN-based ACFs showed the highest formaldehyde adsorption capacity because there are more abundant nitrogen-containing groups, especially pyrrolic, pyridonic, pyridinic, and quaternary on the Surface. The breakthrough time and formaldehyde adsorption capacity of one kind of PAN-ACF were 361 min and 0.478 mmol/g, respectively. 9) 2007 Wiley Periodicals, Inc.