Chemiluminescence (CL) during the n-butylpyridinium bromide-catalyzed decomposition of cumene hydroperoxide was studied. The chemiluminescence intensity in this process substantially depends on the salt and hydroperoxide concentrations. Mathematical simulation of experimental chemiluminescence curves shows that a likely reason for CL generation is the deactivation of excited molecules of two products. These products are formed in different chemical reactions, the rates of which depend on the initial catalyst and hydroperoxide concentrations.