The purpose of this paper is the investigation of the dehydrogenation kinetics of boron nitride films during thermal annealing. BNx:H films on silicon substrates were prepared by remote plasma enhanced chemical vapour deposition at 473 K using a mixture of borazine and helium. IR spectroscopy and ellipsometry were used to characterize the film properties and composition. The films contain a certain amount of hydrogen in B-H and N-H bonds. The breakage kinetics of these bonds is different. The breakage of N-H bonds determines the hydrogen annealing kinetics at 973-1073 K. The low-temperature annealing (673-873 K) of B-H bonds is sensitive to the generation of hydrogen from N-H bonds. Heat treatment leads to ordering of the films.