The present invention relates to a method for improved removal of cations, preferably alkaline earth metals, in particular calcium and barium, from aqueous solutions using chelating resins having aminomethylphosphonic acid groups and iminodimethylphosphonic acid groups having high dynamic absorption capacity for cations at a low residual content of the cations and high regeneration efficiency, and a markedly lengthened loading duration of the chelating resin, to the chelating exchangers themselves, and also to uses thereof.