The photooxidative transformations of resins and asphaltenes in petroleum residues were investigated by IR spectroscopy. In photooxidation, these substances undergo both degradation and condensation. Gaseous products are formed in degradation - hydrogen, low-molecular-weight alkanes, formaldehyde, carbon monoxide and dioxide, and in condensation, highly condensed aromatic structures and oxidation products insoluble in organic solvents are formed.