Irradiation damage studies of lithium oxide (Li20) using optical absorption and electron spin resonance (ESR) methods are reviewed. F+-centers and the defects associated with F aggregate centers were introduced in Li2O irradiated with thermal neutrons and oxygen ions. In addition, colloidal Li metal centers were produced at the high fluences. The production process of the F+-centers was discussed from results of the oxygen-ion irradiation. The recovery behavior of F+-centers was studied by isochronal and isothermal annealing experiments.