The bromination reaction of oligoetherdiol derived from allyl glycidyl ether by two procedures has been studied. It has been shown that one procedure provides monohydroxy conpounds and compounds containing no OH groups along with completely brominated oligoetherdiol. Their formation has been supposed to proceed via cyclodehydrobromination reaction due to elimination of one or two hydrogen bromide molecules from oligoetherdiol to form dioxane and dioxepane cyclic fragments. Conditions for complete bromination of oligodiol with retention of OH group functionality have been determined.