Numerical estimates are carried out which show that the polaronic effects cannot be an origin of specific properties of the CMR materials. A quantum-mechanical calculation of the charge carrier band narrowing with increasing temperature is carried out for the double-exchange systems. Comparing its results with experimental data shows that the hole–phonon coupling in them is too weak for the small polaron formation. Despite this, a giant isotope effect is possible in the manganites due to an isotope dependence of the nonstoichiometry of manganites, to which lattice vibrations contribute considerably.