The distributions of the 13C NMR-measured structural-group composition parameters of the Lena–Tunguska basin crude oils were obtained. All these distributions were shown to be far from normal, many of them being asymmetric and/or bimodal. These oils exhibit a significantly lower content of aromatics than the Volga–Urals and Western Siberia oils. The principal maximum of Car distribution lies in the distribution tail areas of the other two basins. The Lena–Tunguska oils are free of fluids with low content (below 14 abs %) of n-alkyl structures. It was also demonstrated that the crude oils sampled from the basin’s two major tectonic structures, namely the Baikit anteclise and the Nep-Botuob anteclise, differ significantly from one another in the concentrations of aromatics and n-alkyl structures.