New types of poly(ester ether ketone)s 3 and 8 were prepared by three-component polycondensation of bis(diazoketone) 1 with a variety of dicarboxylic acids 2 and THF or THP catalyzed by Rh(2)(OAc)(4). THF was ring-opened and incorporated into almost every carboxyl O-H of 2 via simultaneous insertion together with a diazocarbonyl-derived carbene, resulting in the formation of a unique poly(ester ether ketone) framework. On the other hand, when THP was used as a cyclic ether, insertion of carbene alone into the carboxyl O-H (normal insertion) competes with the simultaneous insertion of THP and carbene, and the ratio of the two modes of insertion depends on the kind of 2 employed. The mode and selectivity of the propagation were confirmed by conducting Rh-catalyzed model reactions of diazoacetophenone 4 with 4-tert-butylbenzoic acid 5 in THF and THP.