AbstractThe types of long‐lived free radicals formed in predried cellulose I and cellulose II, after irradiation in a nitrogen atmosphere at 25°C by γ‐radiation from 60Co, were resolved by selectively scavenging some of the radicals and then recording the ESR spectra generated. The effects of anhydrous ammonia (both gas and liquid), water, solutions of sodium hydroxide, and temperature of heating on the ESR spectra generated by the irradiated celluloses were recorded. Most of the free radicals formed in the irradiated celluloses are apparently trapped in the amorphous or less ordered regions of the cellulosic structure. About 70% of the radicals formed in irradiated cellulose I and about 90% of the radicals formed in irradiated cellulose II are scavenged by contacting the samples with water. The ESR spectra of the free radicals scavenged by water are almost identical for both irradiated celluloses. Contact of the irradiated celluloses with ammonia (liquid) scavenged most of the trapped free radicals. It also appears likely that the long‐lived free radical sites in the highly ordered regions in both irradiated celluloses are the same. As shown by the effects of orientation of irradiated cellulosic fibers in the magnetic field on the ESR spectra recorded, differences in spectra for the irradiated celluloses are probably related to conformations of the trapped radicals which are dependent on differences in crystal lattice types of cellulose I