Packaging industry is responsible for a significant part of the plastic waste generation. Besides polyolefins, poly(ethylene-terephtalate) (PET) used as packaging of soft drinks can be highlighted concerning their volume. Production of polymer blends based on waste resources can contribute to the solution of the urgent recycling issues. In our experiment real industrial waste based PET were studied as the main component of PET/PS, PET/PA and PET/PO blends. Compatibilization between the components is essential because of the weak mechanical properties of blends originated from the coprocessing of plastics. As compatibilizers olefin-maleic-anhydride copolymer based additives have been applied in the form of masterbatches. Matrices of the masterbatches were waste and commercial polyolefins as well. Additive structures differed from each other both in ratio and length of the carbon chains of compounds linked to maleic-anhydride groups. Tensile properties and rheological behaviour of the blends produced as extruded strings and films were studied. Great improvement has been achieved in the mechanical properties of extruded 20/80 PET/PA, since 90 % growth was observed in elongation at break in the presence of masterbatch (polypropylene matrix containing 0.2 % compatibilizer) meanwhile its strength has also improved compared to the sample without masterbatch.