Various kinds of additives are used in a polymer, such as an antioxidant, a light stabilizer, and an ultraviolet absorber. Because a polymer’s properties depend on the additives in the raw material, it is important to understand these additives. Matrix-assistance laser desorption/ ionization time-of-flight mass spectrometer (MALDI-TOFMS) JMS-S3000 SpiralTOF™ is widely used in polymer analysis. High-energy collision–induced dissociation (HE-CID) measurement with the TOF-TOF option is also useful in analyzing the structures of additives. SpiralTOF™ can achieve a high precursor ion selection with a revolution of 17 m. Fragmentation derived from HE-CID can be observed only due to the ions from post-source decay (PSD), these fragment ions can be eliminated by the four electrostatic sectors that constitute the spiral trajectory. In this Applications Note, we report on polymer structural analysis by compare fragmentation patterns in the product ion spectra of IRGANOX 1076 M+・ and [M+Na]+.