A comparative study on the mechanical and dielectric relaxation behavior 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  relaxations located at nearly the same temperature, approximately Ϫ80°C at 1 Hz, followed by ostensible glassrubber or ␣ relaxations centered in the neighborhood of 27, 30, and 125°C for PAMMD, PAMED, and PMAMED, respectively, at the same frequency. The values of the activation energy of the  dielectric relaxations of these polymers lie in the vicinity of 10 kcal mol Ϫ1 , ϳ 2 kcal mol Ϫ1 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 ␣ 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 ␣ and  relaxations at low and high frequencies, respectively. The high conductive contributions to the ␣ 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 ␣ and  absorptions merge together to form the ␣ 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 -prominent relaxations that polymers containing dioxane and cyclohexane pendant 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 ␣ 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.