Modes of U and Th occurrence in coal and peat have been studied. By examples of different fields of Northern Asia, it has been shown that the scattered form of uranium and thorium occurrence dominates in peat and brown coal. Along with the scattered mode associated with organic matter, U and Th form minerals of their own, represented by uraninite, coffinite, and monazite, in brown and bituminous coals and there are minerals in which they are present as an isomorphic accessory (zircon, xenotime, etc.). New data on the ratio between the mineral and organic forms of occurrence of uranium and thorium in coals and peats have been obtained. The change in the mode of U and Th occurrence through the peat-lignite-coal sequence has been revealed.