The paper contains an analysis of the used of Diefallah's composite integral method of kinetic parameters evaluation. It is
shown that the application of this method should be preceded by the application of an isoconversional method through which
the dependence of the activation energy, E, on the conversion degree,a,
should be established. If Edepends ona, Diefallah's composite integral
method leads to erroneous results. If Edoes not depend ona, the
true kinetic model should be comprised in the pre-established set of kinetic models. These observations were checked for two
sets of non-isothermal data, namely: (a) the TG curves corresponding to the dehydration of CaC2O4H2O; (b) the TG curves corresponding to the thermal decomposition of polyvinyl chloride (PVC).