The major objective of this presentation to summarize new regional datasets on the quality and quantity of fossil organic matter (OM) in permafrost sequences of NE Siberia, in order to show the permafrost carbon pool heterogeneity related to paleoenvironmental dynamics, and the improved estimation of permafrost organic carbon stocks. OM stored in Quaternary permafrost grew, accumulated, froze, partly decomposed, and refroze under different environmental condition, reflected in specific biogeochemical and cryolithological features. OM in permafrost is mainly represented by twigs, leaves, peat, grass roots, and plant detritus.