Paraffinic and high-paraffin oils and asphaltene-resin-paraffin (ARP) deposits of Samara oblast have been investigated by differential scanning calorimetry (DSC) and GLC techniques. High-paraffin oils have been found to contain n-alkanes with the number of carbon atoms of C(15)-C(60) and higher forming a crystalline phase with the mp similar to 30-40 degrees C. The ARP deposits from high-paraffin oils almost do not contain high-molecular-weight n-alkanes with the number of carbon atoms >55. This is due to the peculiarities of the crystallization and cocrystallization processes of high polydispersity n-alkanes in crude oils.