Dynamic mechanical and dielectric behaviour of poly(dibenzyl itaconate), and poly(diethylphenyl itaconate) were studied. The study was performed by determining the components of the complex relaxation modulus E* and the complex dielectric permittivity epsilon*. The results are compared with those previously reported for poly(benzyl methacrylate), poly(monobenzyl itaconate) and poly(monoethylphenyl itaconate). The results are discussed in terms of the effect of flexible spacer groups and of the different steric hindrance between mono and disubstituted polymers.