Cross-linked poly(4-vinylpyridine) was converted to its borane complex by different methods. The exchange reaction with BH3-THF; the reaction of boron trifluoride iodine, and bromine polymer complexes; as well as the hydrochloride derivative with sodium borohydride were investigated. Polymers with a high borane content were obtained. The borane content was dependent on the cross-linking level and on the method of preparation. The hydrolytic stability of the borane-bound polymer was higher than that of pyridine-borane. The cross-linked poly(4-vinylpyridine)-borane showed a high degree of stability toward hydrolysis under acidic conditions. Hydrolysis in acidic media was found to be an autoaccelerated reaction.