It was demonstrated that ZrO2 thin films can be grown in the ZrCl4-based atomic layer deposition process at substrate temperatures of 180-600 degreesC. The films grown on silicon and silica substrates were amorphous or polycrystalline dependently on the growth temperature and film thickness. Crystalline films grown at 180-210 degreesC contained a cubic phase of ZrO2. Tetragonal ZrO2 was the main crystalline phase in the films that were 10-50 nm in thickness and were deposited at 300-600 degreesC. In thicker films, grown at 300-600 degreesC, the monoclinic phase appeared and started to dominate with the further increase of film thickness. No significant difference was observed in the phase composition and preferential orientation of films that were grown at the same process parameters on single crystal silicon and amorphous silica substrates. Neither the growth mechanism nor the phase composition of films depended considerably on whether H2O or the commercial aqueous solution of H2O2 (35%) was used as the oxygen precursor.