Bicyclic dioxetane 1 bearing a 3-hydroxyphenyl group underwent thermal decomposition in solution (TDsoln) to form 3-oxopentyl 3-hydroxybenzoate 4 accompanied by the emission of light [λmaxCL (TDsoln)=405nm] due to an excited 3-oxopentyl group in 4. Dioxetane 1 also exclusively gave 4 by thermal decomposition in crystal (TDcryst). However, in contrast to TDsoln, TDcryst of 1 gave light [λmaxCL (TDcryst)=464nm] due to excited oxidobenzoate 3∗ and/or its closely related species formed by CTID (charge-transfer induced decomposition) mechanism. The unique chemiluminescent TDcryst of 1 was presumably the result of hydrogen bonding formed in the crystal between the phenolic proton of a dioxetane molecule and a peroxide oxygen of another dioxetane molecule. In this work, TDcryst as well as TDsoln of bicyclic dioxetane analog bearing a 4-fluorenyl-3-hydroxyphenyl moiety 10 and of adamantylidene-dioxetane bearing a 3-hydroxyphenyl group 5b were also investigated.