Thermoelectric power and XRD of layered VOPO4.2H2O have been studied in dependence on temperature. The results of thermomechanical analysis (i.e. thermal changes of the thickness of the crystal across the layers) correspond to the changes of basal spacing during heating. The values of the dehydration temperatures have been determined. The conductivity caused by positive charge carriers is predominant in vanadyl phosphate hydrates, whereas conductivity in anhydrous VOPO4 is electronic, as it follows from the thermoelectric power measurements.