The invention concerns a radiopaque, non-biodegradable, water-insoluble iodinated benzyl ether of poly(vinyl alcohol) consisting of a PVA having covalently grafted thereon iodinated benzyl groups comprising 1 - 4 iodine atoms per benzyl group, a process for preparing the same comprising reacting a 0 - 100 % hydrolyzed PVA with a iodinated benzyl derivative comprising 1 - 4 iodine atoms per benzyl group in a polar aprotic solvent in the presence of a base in anhydrous conditions. Said iodo-benzylether-PVA is useful as embolic agent in an injectable embolizing composition. The invention also concerns an injectable embolizing composition comprising the iodo-benzylether-PVA and a water-miscible, biocompatible solvent solubilizing the iodo-benzylether-PVA, wherein the concentration of the iodo-benzylether-PVA in the composition is selected in the range of 5 - 65 w/w % so that the composition is capable of forming a cohesive mass upon contact with a body fluid by precipitation of the iodo-benzylether-PVA. Said injectable embolizing composition is particularly useful for forming in-situ a cohesive mass in a blood vessel or into a tumor
