Properties of thermal vacancies in CoSi2 and defects in electron irradiated and proton irradiated CoSi2 have been studied by positron lifetime spectroscopy. It has been found that thermal vacancies in CoSi2 are easily quenched in. The effective formation enthalpy of vacancies has been estimated to be about 1.1 eV. The recovery of electron irradiated CoSi2 occurs in two stages; the first stage around 310 K attributed to the migration of vacancies forming secondary defects and the final stage between 670 and 700 K, where the secondary defects dissolve. Since the positron lifetime at the secondary defects is smaller than that at vacancies, the secondary defects must be collapsed vacancy clusters, such as faulted dislocation loops. In the recovery of proton irradiated CoSi2, microvoids, which are annealed out above 820 K, as well as collapsed vacancy clusters are also formed. The three dimensional vacancy clustering is probably due to the existence of implanted hydrogen atoms.