An investigation has been made of the X-ray phase composition of various types of crude oil and their components - oils, resins and asphaltenes. It has been established that the main component of all crude oils is the polynaphthene phase (N(ph)). The different resin fractions and asphaltenes, besides N(ph), contain a graphite-like phase G(ph), the concentration of which increases from resins to asphaltenes. N(ph) and G(ph) in the various resin fractions and asphaltenes are in certain quantitative ratios, the values of which hardly change as a function either of the age or the depth of occurrence of the crude oils. In paraffinic crude oils and their asphaltenes there are solid paraffins of normal structure and with rhombic crystal systems.