The present invention relates to the use of at least one 2-methylsuccinic acid diester derivative of formula (I) below:in a composition comprising, in a cosmetically acceptable medium, at least one liquid fatty phase and at least one lipophilic active agent, for dissolving the said active agent in the said liquid fatty phase and/or for improving the solubility of the said active agent in the said solid fatty phase. The present invention relates especially to a composition comprising, in a cosmetically acceptable medium, at least one liquid fatty phase, characterized in that it contains at least one 2-methylsuccinic acid ester derivative of formula (I) and at least one lipophilic active agent.
