  Recently Yampol'skii et al. [Phys. Rev. A v.82, 032511 (2010)] advocated that
Lifshitz theory is not applicable when the characteristic wavelength of the
fluctuating electromagnetic field, responsible for the thermal correction to
the Casimir force, is larger than the size of the metal test bodies. It was
claimed that this is the case in experiments which exclude Lifshitz theory
combined with the Drude model. We calculate the wavelengths of the evanescent
waves giving the dominant contribution to the thermal correction and we find
that they are much smaller than the sizes of the test bodies. The opposite
conclusion obtained by the authors arose from a confusion between propagating
and evanescent waves.
