A comparative study on the mechanical and dielectric relaxation behaviour of poly(5-acryloxymethyl-5-methyl-1,3-dioxacyclohexane) (PAMMD), poly(5-acryloxymethyl-5-ethyl-1,3-dioxacyclohexane) (PAMED), and poly(5-methacryloxymethyl-5-ethyl-1,3-dioxacyclohexane) (PMAMED) is reported. The isochrones representing the mechanical and dielectric losses present prominent mechanical and dielectric beta relaxations located at nearly the same temperature, approximately -80 degrees C at 1 Hz. followed by ostensible glass-rubber or alpha relaxations centered in the neighbourhood of 27, 30, and 125 degrees C for PAMMD, PAMED, and PMAMED, respectively, at the same frequency. The values of the activation energy of the beta dielectric relaxations of these polymers lie in the vicinity of 10 kcal mol(-1), similar to 2kcal mol(-1) lower than those corresponding to the mechanical relaxations. As usual, the temperature dependence of the mean-relaxation times associated with both the dielectric and mechanical alpha relaxations is described by the Vogel-Fulcher-Tammann-Hesse (VFTH) equation. The dielectric relaxation spectra of PAMED and PAMMD present in the frequency domain, at temperatures slightly higher than T-g, the alpha and beta relaxations at low and high frequencies, respectively. The high conductive contributions to the alpha relaxation of PMAMED preclude the possibility of isolating the dipolar component of this relaxation in this polymer. Attempts are made to estimate the temperature at which the alpha and beta absorptions merge together to form the alpha beta relaxation in PAMMD and PAMED. Molecular Dynamics (MD) results, together with a comparative analysis of the spectra of several polymers, lead to the conclusion that flipping motions of the 1,3-dioxacyclohexane ring may not be exclusively responsible for the beta-prominent relaxations that polymers containing dioxane and cyclohexane pendent groups in their structure present, as it is often assumed. The diffusion coefficient of ionic species, responsible for the high conductivity exhibited by these polymers in the alpha relaxation, is semiquantitatively calculated using a theory that assumes that this process arises from MWS effects, taking place in the bulk, combined with Nernst-Planckian electrodynamic effects, due to interfacial polarization in the films.