Tetrafluoromethane, CF4, is markedly less soluble in water than methane and neopentane around room temperature: it is a superhydrophobic solute. An analysis of the physical origin of this superhydrophobicity is performed, exploiting literature thermodynamic data covering the 5-55 degrees C temperature range. It results that the CF4-water dispersion interactions are markedly weaker in magnitude than those of a 'hypothetical' hydrocarbon having the same size of tetrafluoromethane, providing a smaller counterbalancing effect of the work spent to create the cavity in water. The weakness of the CF4-water dispersion interactions is due to the very small polarizability of CF4, which, in turn, is caused by the strong electronegativity of fluorine atoms. (c) 2008 Elsevier B. V. All rights reserved.