The structure and composition of surface layers formed on different Zr-alloys during corrosion in high pressure water with different Li+ content at 360 degrees C were investigated by X-ray diffraction, Raman spectroscopy and metallography. X-ray diffraction of surface layers clearly demonstrated the existence of the monoclinic form of ZrO2 which showed the strong preferred orientation (0 0 2) and significant broadening of reflections due to microstrain in layers or small crystallite size, The existence of tetragonal form could not be undoubtedly proved by X-ray diffraction and had to be verified using Raman spectroscopy. The coating thickness was determined by metallography, weight gain due to metal/oxide transformation and absorption of X-ray radiation. The results obtained gave acceptable agreement for layer thickness determined by weight gain and metallography while those from X-ray diffraction show 10-20% deviation.