AbstractA qualitative description is given to account for general picture of changes in properties of two types of polymer compositions–filled with fillers of high free surface energy and with polymeric fillers, or polymer‐polymer mixtures. It was shown that the properties of the surface layers are different in comparison to polymer in bulk as a result of interactions at the interface and changes in conditions of mass transfer during the process of structure formation. Depending on the conditions of surface layers formation, their structure and polymer‐filler ratio, various types of compositions arise. For polymer‐polymer mixtures there are various states of their structure depending on the thermodynamic compatibility of components in melt and cooling conditions and phase separation. An important role of small amount of the addition polymer in the properties of binary composition is shown as well as the role of low molecular weight homologues and admixtures in the processes of the structure fo