A series of new polyetherketones was prepared by Rh-catalyzed polycondensation of bis(diazocarbonyl) compounds 1a-c with aromatic diols 2A-C in cyclic ethers (THF, THP, and 1,4-dioxane). In addition to the expected insertion of diazo-bearing carbon of I a c into O-H of 2A-C releasing N-2, unexpected incorporation of the ring-opened cyclic ethers between the diazo-bearing carbon of I a c and phenolic oxygen of 2A-C occurred, providing the polymer main chains with additional oxyalkylene units. The extent of-cyclic ether incorporation relative to the expected insertion depended on the kind of the cyclic ether: THF, 95-98%; THP, 26-32%; 1,4-dioxane, 11-21%. Polyetherketones with a variety of main chain structures can be prepared by the new polycondensation.