The intention of this diploma thesis is to analyze thermal recovery of plastic waste and their tertiary and quaternary recycling, focusing on polyethylene terephthalate (PET). The thermal stability of PET was determined by the thermo-gravimetric analysis. By low temperature pyrolysis was found that the highest share was represented by a solid residue, which was influenced by a temperature of the process. The GC-MS analysis assessed the chemical composition of a PET sample and the proportion of its individual compounds.