A DTBP-promoted C–H selenation of aldehydes with diselenides under metal-free and solvent-free conditions is described. This system shows good functional group compatibility, functional groups including bromo, trifluoromethyl, chloro, amine and heterocycle-containing moieties including thiophene and furan are all tolerated by the reaction conditions employed. Both diaryl and dialkyl diselenides reacted smoothly with aldehydes to provide selenoesters in good to excellent yields.