In this study, steam reforming of acetic acid, ethylene glycol, acetone, ethyl acetate, m-xylene, and glucose, which were representative of the main components in bio-oil, were performed to investigate the feasibility of these feedstocks for hydrogen production. The effects of reaction temperature and steam to carbon ratios (S/C) on steam reforming as well as coke formation tendency of the bio-oil components in the presence and absence of steam were investigated in a detailed manner. Low reaction temperature and S/C led to low steam reforming efficiency, and consequently decomposition or degradation of the feedstocks dominated, resulting in large amounts of by-products. Increasing reaction temperature and S/C increased the steam reforming rates and the partial pressure of steam on catalyst surface, favoring conversion of the feedstocks and removal of the by-products. Coke formation rates of the feedstocks during the long-term experiments decreased in the following orders: glucose >> m-xylene > acetone > ethyl acetate > ethylene glycol > acetic acid. Decomposition or polymerization of the feedstocks to carbonaceous deposit was the main route for coke formation in glucose, m-xylene, and acetone reforming, while the large amounts of by-products such as ethylene, CO, or acetone were main sources of coke in the steam reforming of ethyl acetate, ethylene glycol, and acetic acid. (C) 2008 Elsevier B.V. All rights reserved.