Poly(aryl ether ether ketone) (PEEK) films irradiated with 2 MeV O+ and Ar+ ions to fluences in the range 10(11)-10(13) cm(-2) were treated with 5 mol/L LiCl aqueous solution at 100degreesC for 1 h. After removal of excessive, weakly bound LiCl the samples were annealed at temperatures from 50 to 250degreesC for 1 h to check the mobility of the incorporated LiCl. The amount of incorporated LiCl and its depth profile were determined using the neutron depth-profiling (NDP) technique, which makes use of the Li-6(n(th), He-4) H-3 nuclear reaction. Up to the maximum annealing temperature no significant escape of the LiCl was observed. With increasing annealing temperature, a gradual migration of LiCl dopant toward the sample surface was observed on the irradiated PEEK samples.