In a method of packaging radioactive anion and/or cation exchange resin particles for shipment or storage wherein the resin particles are added to a cement mixture so as to form a cement matrix and the cement matrix is then allowed to solidify, the improvement comprising adding a chemically affecting additive to said resin particles and/or heating said resin particles prior to or during the solidification of said cement matrix to reduce their swelling factor to below 1.7, said swelling factor representing the quotient of the settled volume of said resin particles in a water-moistened, swelled state and the settled volume of said resin particles in a dry state, thus reducing the swelling and shrinking properties of said resin particles to such an extent that an increased amount of said resin particles can be added to said cement mixture per unit volume without reducing the water resistance of the solidified cement matrix to an unacceptable level.