Optically pure phosphoroselenoyl chloride reacted with Et3N in the presence of H2O to give a phosphoroselenoic tertiary ammonium salt. Formation of the salt was confirmed by X-ray molecular structure analysis. The quaternary ammonium salt was prepared by reacting phosphoroselenoic acid O-2-silylethyl ester with Bu4NF. The alkylation of tertiary ammonium salt with racemic alkyl halides gave phosphoroselenoic acid Se-esters as diastereomeric mixtures. The cleavage of Se-esters with Bu4NF gave optically active dialkyl diselenides.