The current work describes the development of a CZE method with quadrupole QTOFMS detection and UV detection for the quantitation of Cyasorb 3529, a common hindered amine light stabilizer (HALS), in polymer materials. Analysis of real polymer samples revealed that the oligomer composition of Cyasorb 3529 changes during processing, a fact hampering the development of a straightforward method for quantitation based on calibrationwith aCyasorb 3529 standard. To overcome this obstacle in-depth investigations of the oligomer composition of this HALS using QTOF-MS and QTOF-MS/MS had to be performed whereby 22 new oligomer structures, in addition to the ten structures already described, were identified. Finally, a CZE method for quantitative analysis of this HALS was developed starting with a comprehensive characterization of a Cyasorb 3529 standard using CZE-QTOF-MS, subsequently allowing the correct assignment of most Cyasorb 3529 oligomers in an electropherogram with UV detection. Employing the latter detection technique and hexamethyl-melamine as internal standard, peak areas obtained for the melamine could be correlated with those from the triazine ring, the UV-absorbing unit present in the HALS. This approach finally allowed proper quantitation of the single oligomers of Cyasorb 3529, an imperative for the quantitative assessment of this HALS in real polymer samples.