Abstract <p>The quenching of the long-lived phosphorescence of naphthalene–β-cyclodextrin–cyclohexane ternary complexes localized in the matrix of β-cyclodextrin–cyclohexane binary complexes in an aqueous suspension of crystal hydrates and in a powder formed after drying of the crystal hydrates has been studied. In the suspension, the phosphorescence kinetics is monoexponential, and dynamic quenching takes place; the bimolecular quenching constant is <i>k</i>_q = 0.95 × 10⁵ s⁻¹ M⁻¹. In the powder, the phosphorescence kinetics is not monoexponential; this fact is apparently attributed to the heterogeneous structure of the environment of the naphthalene molecules. The heterogeneity of the environment is evidenced by the presence of a distribution of nonradiative process rate constants and a decrease in the accessibility of naphthalene molecules for interaction with oxygen.</p>