A series of novel fluorene moiety-containing polycarbonates was synthesized by the anionic ring-opening polymerization of six-membered spirocyclic carbonates possessing 9,9-fluorene groups at the 5,5-position. The polymers could be considered cardo-type polymers because they had 9,9-fluorene groups as a loop-shaped side chain. Interestingly, the fluorene pendant polycarbonates were obtained in sufficiently high molecular weights and in good yields, although the monomers were structurally closely related to the 5,5-diphenyl-substituted cyclic carbonate that exhibited very low polymerizability. Furthermore, the polymerizations of substituted fluorene-based six-membered spirocyclic carbonates were investigated. All of the obtained polymers showed favorable properties, including good solubility, amorphous natures, favorable thermal stabilities, remarkably low birefringence values and high refractive indices despite consisting only of C, H and O atoms. The good potentiality in the application to optical materials was shown here. A series of novel fluorene-based cardo polycarbonates was synthesized by the anionic ring-opening polymerization of six-membered spirocyclic carbonate monomers. The polymers possessed a fluorene skeleton placed perpendicularly to the main chain. The polymerization of the fluorene monomers progressed according to their solubility in the reaction solvent. Interestingly, the fluorene pendant polycarbonates were obtained in sufficiently high molecular weights and in good yields, in spite of the fact that the monomers are structurally closely related to the diphenyl-substituted cyclic carbonate, which exhibited very low polymerizability. All obtained polymers showed favorable properties, including good solubility, amorphous nature, favorable thermal stabilities, remarkably low birefringence values and high refractive indices despite of the polymer consisting only of C, H and O atoms. The good potentiality in the application to optical materials was shown here.