We report herein the synthesis of enantiomerically pure 2-phenyl- and 2-ethyl-2-trifluoromethylaziridines by Mitsunobu-type cyclisation of the corresponding N-protected amino alcohols, and our results regarding their ring opening with selected nucleophiles. Under basic conditions, N-tosyl aziridines have been regioselectively opened at the less hindered carbon. Under acidic conditions, the regioselectivity of the attack depends on the nature of the substituent at C-2 and on the nitrogen protecting group.