Relaxation processes in ZrO2 have been studied at pressures in the range of 22-50 GPa by measurements of high-pressure electrical relaxation of resistance in time. Electrical relaxation in nanocrystalline praseodymium doped zirconia powders and in a bulk material sample of zirconia has been measured in the pressure range from 35.5 to 50 GPa. The time dependence of electric resistance is most precisely described by exponential function up to the pressure of 35.5-50 GPa. The time dependence of electric resistance is most precisely described by exponential function up to the pressure 44-45.5 GPa. After treatment the pressure higher than 45.5 GPa, the character of the relaxation changes and resistance increased with time. Relaxation processes have not been observed in ZrO2 with 56 nm crystallite sizes.