We study the role of ethanol in the thermolytic synthesis of multiwalled carbon nanotubes. We show that low concentrations of ethanol control the length and diameter, as well as the crystalline quality of the produced nanotubes. We statistically evaluated the dimensions of the tubes as the concentration of ethanol is increased. The quality of the samples results in more crystalline products when low concentrations of ethanol (similar to 1-2%) are used in the experiments. In addition, the introduction of ethanol during the synthesis seems to incorporate coordination groups on the surface of nanotubes that cause an enhanced reactivity and a better solubility. (C) 2008 Elsevier B.V. All rights reserved.