The study addresses the structure of the lithosphere of Siberia, including the Siberian Craton and the West Siberian Basin, with a particular focus on the crustal structure of the entire region and the density structure of its lithospheric mantle. The first part of the study included the development of a new regional crustal model, SibCrust, that is a digital crustal model for both the Siberian Craton and the West Siberian Basin. The SibCrust model, constrained by digitizing of all available seismic profiles and crustal velocity models across the Siberia, also includes a critical quality assessment of regional seismic data and crustal regionalization based on seismic structure of the crust. The second part of the study included the development of the SibDensity model that is the density model of the lithospheric mantle calculated by the mass balance method. Mantle density modeling involved calculation of the crustal correction based on the SibCrust model. The SibDensity model is made of two independent parts calculated for two major tectonic provinces with contrasting geodynamic evolution: the West Siberian Basin and the Siberian Craton. The modeling results, that are lateral variations in the lithospheric mantle density, are interpreted in terms of regional tectonic evolution, namely the mechanism by which the Paleozoic intracontinental basin has been formed and the tectono-magmatic processes by which the Archean-Proterozoic craton has been modified as reflected in the composition of its mantle.