The temperature‐frequency dependence of dielectric parameters for several PVC‐plasticizer systems and PVC blends was obtained. Kinetic and activation parameters and α‐relaxation spectra were estimated. The increase of the polar group number and size in the plasticizer molecules results in the narrowing of the relaxation spectra and in the increase of inner mobility of PVC segments. It was found for PVC‐ABS and PVC‐Paraloid blends that all relaxation characteristics depend on the miscibility of components. The results were also confirmed by the cloud point data.