The effect of the substrate size on the properties of carbon coatings that are deposited on the glass cylinder substrates by thermal chemical vapor deposition is investigated. Experimental results show that the deposition rate of carbon coatings decreases as the diameter of the glass cylinder increases, because the residence time of the precursor gas in the deposition zone decreases and the deposition area of the substrate increases. Experimental results also reveal that the surface roughness and electrical resistivity of carbon coatings decrease as the diameter of the glass cylinder increases, while the degree of ordering and crystallite size of the carbon coatings increase. (C) 2009 Elsevier B.V. All rights reserved.