The present disclosure relates to radiopaque PVA polymers where the PVA has a first pendant group and a second pendant group, wherein the first pendant group comprises a first phenyl group bearing 1 to 5 iodine atoms, and the second pendant group comprises either (a) a second phenyl group bearing 1 to 3 substituents selected from the group W and optionally 1 to 4 iodine substituents, the group(s) W and the optional iodines being the sole substituents of the second phenyl group. Each W is selected from —OH, —COOH, —SO3H, —OPO3H2, —O—(C1-4alkyl), —O—(C1-4alkyl)OH, —O—(C1-4alkyl)R2, —O—(C2H5O)qR1—(C═O)—O—C1-4alkyl and —O—(C═O)C1-4alkyl; wherein R1 is H or C1-4 alkyl; R2 is —COOH, —SO3H, or —OPO3H2; q is an integer from 1 to 4; wherein the group W may be in the form of a pharmaceutically acceptable salt; or (b) a pyridyl group; which is optionally in the form of a pyridinium ion.