Dielectric and viscoelastic relaxation measurements have been carried out on poly(2-chloroethyl diitaconate) (PDCEI) and poly(3-chloropropyl diitaconate) (PDCPI) between 123 K and temperatures about 293 K above the glass transition temperatures. The two polymers exhibit three peaks, a gamma-relaxation in the range from 133 to 193 K (at 1 Hz), a broad beta-process, in the range from 193 to 293 K and a third peak observed in mechanical measurements at 323 K (PDCEI) and 293 K (PDCPI) probably corresponding to the alpha dynamic glass transition phenomena. In dielectric measurements, conductive contributions overlap the alpha-relaxation precluding the observation of peaks at temperatures above room temperature. The apparent activation energies for the gamma-relaxation according to the mechanical and dielectric measurements are close to the values derived from the empirical force field molecular mechanics calculations. A comparison is made between the relaxational data of PDCEI and PDCPI by one hand and poly(di-n-propyl itaconate) (PDPI) and poly(di-n-butyl itaconate) (PDBI) by other. This comparison allows us to conclude the relevant role played by the chlorine atoms not only in the gamma relaxations but also in the beta relaxations of PDCEI and PDCPI. (C) 2004 Elsevier Ltd. All fights reserved.