The temperature dependences of elastic and relaxation properties of films of salt and base forms of chitosan were obtained by methods of dynamic mechanical analysis. It was estimated that the presence of two maxima on the temperature dependence of mechanical loss tangent tanδ at T1 = 150–160°C and T2 = 250–270°C is typical of the salt form of chitosan. The maximum at 150–160°C on tanδ curves is reduced or even eliminated after thermal or alcohol–alkali treatment of chitosan acetate films, while the high-temperature maximum is preserved. The results of IR spectroscopy and thermogravimetric analysis allow supposing that the low-temperature maximum of molecular mobility in films of chitosan salt form is related to the removal of absorbed water and residues of acetic acid as well as to dehydration of macromolecules. The maximum at 259°C determines the glass transition temperature of the chitosan base form.