Molecular dynamics of six side-chain liquid-crystalline polymethacrylates with phenylbenzoate mesogenic groups having tail groups of different lengths was investigated by dielectric spectroscopy (DS) and by thermally stimulated discharge current (TSDC) methods. In the temperature range from room temperature to 160degreesC, three processes of relaxation of dipole polarization, the beta(1), alpha, and delta processes, were revealed. These correspond, from low to high temperatures, to the mobility of ester groups adjoining the backbone, to the segmental motion, and to the mesogenic group orientation about its short axis. For a quantitative analysis, dielectric spectra were described by a superposition of one or of two Havriliak-Negami functions and of a conductivity term. It was shown that the molecular mobility of the observed relaxation processes does not depend on the mesogen tail length. The comparison of the DS and TSDC data with each other gives good agreement between the temperature position of dielectric loss peaks at the equivalent frequency of TSDC measurements and the temperature position of depolarization current maximum. By using thermal windowing techniques, the activation parameters for the observed processes were determined.