The theoretical basis of thermally stimulated depolarization (TSD) and thermally stimulated currents (TSC) methods have been discussed. It has been shown that the application of these techniques to polymers allows an analysis of complex dielectric relaxation processes in polar polymers as well as an estimation of processes related to the release of injected and trapped carriers in high molecular weight substances. The discussion of some results obtained with TSD and TSC techniques for poly(N-vinylocarbazole) and poly(ethylene terephtalate shows that the characteristic changes of TSD and TSC spectra as well as characteristic parameters calculated depend on the supermolecular structures arising in these materials; thus these methods may give new information on the structures in polymers and their changes due to the thermal treatment.