The distribution of organic carbon in the Bazhenov horizon rocks of the western Siberian sedimentary basin is investigated. The organic carbon concentration in rocks is estimated by the results of core analyses (4094 core analyses) and by the calculations of the core-log data correlations (48 500 measurements) according to the data of radiation and electrical loggings. The average content of organic carbon in the rocks of the Bazhenov and Tutleim (lower subformation) formation is 7.7%. The map of organic carbon concentrations in the sedimentary rocks of the basin is constructed. In the basin, Corg is distributed asymmetrically. The region of maximum Corg concentrations occupies the southwestern part of the internal area of the sedimentary basin. Silicites and biogene silica-enriched mixtites are enriched with organic matter most of all.