In the present study, thermal degradation of polyolefins (PP and LDPE) and PET in a tubular reactor in an inert atmosphere was conducted. Each polymer was subjected to pyrolysis at the temperatures of 673, 773, 873, and 973 K. Yields of tar, residual coke and gas, and conversion degrees were calculated. Tars which include valuable chemicals were characterized by GC-MS, H-1-NMR, FTIR, and GPC. Pyrolysis gases (C1 + C2, C3, C4, C5, and C6 + C7) were also analyzed by GC analysis. From the comparison of data, it can be said that pyrolysis of PP and LDPE leads to the formation of tar containing mainly paraffinic structures, while aromatic structures were produced by the pyrolysis of PET.