Studies were made on behaviors of riboflavin, FMN and FAD on various anion exchange resins as a preliminary experiment for elimination of cyclic-FMN from FAD preparations. It was found that FMN and FAD were easily adsorbed on any kind of anion exchange resins, while adsorption of riboflavin on these resins hardly occurred. A remarkable difference was, however, observed between behaviors of FMN and FAD on such resins as Dowex-2 (Cl), Amberlite IRA-411 (HCOO) and IRA-400 (CH_3COO). This results suggests that these resins are useful for elimination of cyclic-FMN from FAD preparations, since cyclic-FMN has been known to have similar properties as FMN.