A B3LYP computational study of the reaction of a methylperoxy radical with alkyl aminoethers has been performed, which represents a key step in polymer stabilization promoted by hindered-amine light stabilizers (HALS). In the most realistic model studied, a nitrogen oxidation mechanism is favored with respect to the S(H)2 process known as the Denisov reaction. Nonetheless, the activation energy difference for the two reactions is less than 3 kcal/mol. We suggest that both mechanisms contribute to HALS-promoted polymer stabilization.