Vacancies and their clusters have been studied in electron or proton irradiated α 2 Ti 3 Al phase by using positron annihilation lifetime spectrometry. No constitutional vacancies have been detected in the material; all constitutional point defects are substitutional anti-site atoms. The irradiated material recovers in two major stages. The first stage, around 250 K, is ascribed to the migration of Ti vacancies, and the second stage, above 350 K, is attributed to the free migration of vacancies at both sites. In sharp contrast with TiAl and Al 3 Ti, microvoids are formed as a secondary defect in electron irradiated Ti 3 Al, which is most likely due to hydrogen atoms dissolved in. Proton irradiation promotes the formation of microvoids in Ti 3 Al. Electron or proton irradiated Ti 3 Al specimens recover almost to the fully annealed state below 700 K.