In the present work the thermally stimulated currents technique was used to study the upper glass transition relaxations in two side-chain liquid crystalline polysiloxanes. The nature of those relaxations at the molecular level is a controversial subject, but our results lead us to suggest thay they correspond to the reorientational motions in the liquid crystalline phase of the longitudinal and transverse components of the dipole moment of the mesogenic side group. This assignment is compatible with the conclusions from extensive studies of the dipolar relaxation behaviour of side-chain liquid crystalline polymers by dielectric relaxation spectroscopy.