Single crystals of sodium salt of guanosine dihydrate and 9 Ethyl Guanine were X-irradiated with the objective of identifying the radical products. Study with K-band EPR, ENDOR, and ENDOR-Induced EPR techniques indicated at least four radical species to appear in both crystals in the temperature range of 6K to room temperature. Three of these radicals (Radicals R1, R2, and R3) were present immediately after irradiation at 6K. Computational chemistry and EPR spectrum simulation methods were also used to assist in radical identifications. Radical R1, the product of net hydrogen addition to N7, and Radical R2, the product of electron loss from the parent molecule, were observed in both systems. Radical R3, in Na⁺.Guanosine^-.2H₂O, is the product of net hydrogen abstraction from C1' of ribose group and radical R3 in 9EtG was left unassigned due to insufficient experimental data. Radical R4, the C8-H addition radical, was also detected in both systems. For Na⁺.Guanosine^-.2H₂O, R4 was observed after warming the irradiated crystals to the room temperature. But for the 9EtG crystals the corresponding radical form was detected after irradiation at room temperature.