The aim of this work is to study the merging of the main alpha and the secondary beta relaxations in poly(butyl acrylate)-i-poly(methyl methacrylate) sequential interpenetrating networks in comparison to net-poly(butyl acrylate)-co-poly(methyl methacrylate) random copolymer networks. In both cases 10% of ethylene glycol dimethacrylate was used as cross-linking agent. The cross-linking density of these networks is high enough to force a certain degree of compatibility of the IPNs, as shown by dynamic-mechanical analysis and thermally stimulated depolarization currents, TSDC. Dielectric relaxation spectroscopy was used to characterize the relaxation behavior in the frequency domain. The strength of the alpha dielectric relaxation in poly(methyl methacrylate) network is small and the merging with the beta relaxation is not apparent in the experimental frequency range. On the contrary, in poly(butyl acrylate) networks it is the strength of the secondary relaxation which is small compared to that of the a relaxation and the relaxation spectrum has the characteristics of the latter in the whole experimental temperature interval. In the copolymer networks, the introduction of butyl acrylate segments in the polymer chains shifts the a process toward lower temperatures with respect to poly(methyl methacrylate) and increases the relaxation strength of the alpha relaxation. The crossover region is shown in copolymers with methyl methacrylate content ranging between 20 and 60 wt %. Nevertheless, in the IPNs with similar compositions the relaxation spectrum shows the characteristics of a secondary relaxation. This behavior is ascribed to the fact that the glass transition of the IPN is dispersed in an extremely broad temperature range, so its relaxation strength at each temperature is quite small, being not significant in comparison to that of the beta relaxation.