The ketonic part of soil lipids was studied in a hydromorphic forest-podzol. The undecomposed forest litter layer (L) and the fragmented mycelium-invaded litter layer (F), and the soil A1 horizon were sampled and analyzed for total lipid and total ketone contents. Total ketones were separated into methylketones and triterpenic ketones. Extractable ketones were not observed in the L layer, but were determined in the F layer of the soil litter. From the F litter layer to the soil A1 horizon, the portions of the two types of ketones, mainly the methylketones, decreased sharply. These last components, which are not primarily plant substances, originated essentially from the β-oxidation of n-alkanes, and the amount of transformation of n-alkanes into methylketones was in inverse ratio to their carbon number. Triterpenic ketones were the dominant part of soil ketones, and all their identified components were of plant origin. An important decrease of the amount of triterpenic ketones was observed from litter to soil, but their decomposition processes were not clearly determined.