The present invention relates to polyacetal polymers which comprise repeating structural units of formula (I), being each of these repeating structural units equal or differentwherein at least one of the repeating structural units of formula (I) contains a group W selected from a triiodobenzene derivative biradical of formula (II) and of formula (III)The invention also refers to a process for their preparation, to compositions comprising them, and to their use as contrast agents, especially for cancer diagnostic.
