Solubilization of three typical perfume compounds, d-limonene (LN), beta-ionone (IN), and geraniol (GL), in the discontinuous micellar cubic (I-1) phase of the water-polyoxyethylene dodecyl ether (C12EO25) system was investigated by phase study and small-angle X-ray scattering (SAXS). The hydrocarbon perfume LN increases the maximum melting temperature of the Il phase, whereas GL decreases it. This phenomenon is related to their solubilization location in the micelle. LN tends to be solubilized inside the aggregates and makes a perfume core (swelling). On the other hand, GL is solubilized in:the surfactant palisade layer and expands the effective cross-sectional area per surfactant,as (penetration). The penetration tendency is in the order GL, IN, and LN,judging from the SAXS analysis. The change in repulsion between hydrophilic moieties of surfactant upon addition of perfume is evaluated by calculating an optimum cross-sectional area, a(S,opt), at which the EO chain is neither compressed nor expanded. It is found from the calculation of a(S)/a(S,opt) that the repulsion considerably increases in the LN system whereas it decreases in the GL system.