ESR investigations show that two‐photon excitation and x irradiation of nominally pure LiNbO3crystals at 20 K create electrons, which are self‐trapped as Nb4+, and holes, which are captured at acceptor‐type defects as O−. The radiation‐induced absorption at low temperatures is attributed to these centers. The trapped electrons and holes play an important role in the two‐photon‐induced photorefractive process.