Results of dielectric studies of lutetium sesquioxide layers examined in Al/Lu2O3/Al thin film sandwiches are reported. The dielectric measurements were carried out in the frequency range 10−5–107Hz and for temperatures from 292K to 500K. Results are presented as plots of frequency functions: the capacitance, the dielectric loss factor, tanδ(f) and also on the complex plane as Cole–Cole plots and Nyquist plots. The influence of the external voltage on C(U) and tanδ(U) was examined. Experimental data were analyzed taking into account thin insulating Lu2O3 film, near-electrode regions of Al/Lu2O3 and Lu2O3/Al interfaces and series resistance of electrodes and leads. The parameters of Lu2O3 film, near-electrode regions and resistance of contacts and leads were determined.