Using an ultra-high vacuum kinetics technique, we present unexpected experimental evidence that thick layers of carbon nanotubes (CNTs) show adsorption behavior that is kinetically distinct to that of thinner CNT films. Thick layers reveal much greater desorption temperatures (binding energies) for n-pentane and benzene compared to thinner CNT films. These results are significant in gaining an understanding of the interplay of kinetics and electronic effects as well as for applications in catalysis. (C) 2009 Elsevier B. V. All rights reserved.