The detailed composition description of poly(ethylene terephthalate) (PET) pyrolysis products still remains a challenge due to the complexity of the obtained mixture. In this context, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses by negative ion electrospray ionization (-) ESI and positive ion laser desorption ionization (+) LDI were performed for characterizing waxy products and solid residues, respectively. (-) ESI FT-ICR MS revealed that the DBE of waxy compounds ranges from 5 to 20 and the carbon number from 7 to 30. Terephthalic acid was the dominant peak in the low m/z range, and 1,4-benzenedicarboxylic acid, 1,2-ethanediyl ester was evidence at higher m/z value. Based on the oxygen atom number, the waxy products displayed seven class compounds. The most significant contributions were observed for O-4 and O-8 species. van Krevelen plots revealed that the most abundant aromatic species followed a monotonous behavior (alignment according to a straight line), highlighting the presence of homologous series. The analysis of the solid residue by (+) LDI FT-ICR MS showed that three classes of compounds were observed: oxygenated compounds, carbonaceous materials, and hydrocarbons. As the temperature increased, the solid residue tended to be associated to a homogeneous structure consisting of fullerene clusters C-n (with n ranging from 30 to 96 at 410 degrees C and from SO to 106 at 480 degrees C). C-60 was systematically the most abundant fullerene.