Two kinds of itaconamic esters, alpha-substituted acrylate derivatives (IAE-I) and alpha-substituted acrylamide derivatives (IAE-II), as well as itaconamides (IAm) were prepared and polymerized with a radical initiator. It has been revealed that N,N-disubstituted IAE-I as an acrylate is more reactive in polymerization than N,N-disubstituted IAE-II as an acrylamide and that N,N’-dialkyl substituted IAm homopolymerizes but N,N,N’,N’-tetraalkyl substituted one does not. In radical copolymerization with styrene, IAE-1 showed a higher polymerization reactivity than IAE-II. The effects of the N-substituents on the polymerization reactivity were discussed on the basis of conformation of the monomers. The polymers obtained were also characterized.