The rates of the competitive photo-sensitized oxygenation of 2-isobutylideneadamantane (1) and 2-propylidene-adamantane (2) with 1, 1-di-t-butyl-2-methoxyethane (3) in various solvents were determined. The rates for 1 and 2 were independent of solvent, whereas that for 3 varied markedly with solvent polarity. Compounds 1 and 2 gave only hydroperoxides while 3 gave dioxetane. These results are interpreted in terms of two competing processes involving little and much charge separation leading to hydroperoxide and dioxetane, respectively.