Chemiluminescence is the emission of light as a result of chemical reaction. The 4-membered dioxetane ring is also proposed as an intermediate in the chemiluminescent reactions. Bisadamantylidene Adamantane 1,2-Dioxetane (BAAD) have received special attention. The former is a very stable compound having half-life time of approximately 104 years at room temperature. The main aim of this study was to investigate the mechanism of chemiluminescent decomposition of dioxetane derivatives BAAD. The ground and the transition states in the closed shell singlet state were optimized by B3LYP/6-31G method.