A study on the deep HDS of light and heavy gas oils produced from Hungarian and Russian crude oils on NiMo/Al 2O 3/promoter catalyst is presented. The effect of sulfur compound distribution of feeds determined by sulfur specific GC on the HDS efficiency is discussed. Kinetical features of desulfurization of different feedstocks are also determined. Conversion of dibenzothiophene (DBT) and its derivatives a real process conditions are studied, and their relative reactivity determined. The advantageous process parameters for producing diesel fuels blending components with low sulfur content are determined. Under optimum process parameters products with sulfur content < 10 ppm from both light gas oils and from heavy gas oil produced from Hungarian crude can be produced. The HDN and aromatic content reduction are also investigated. This is an abstract of a paper presented at the 7th World Congress of Chemical Engineering (Glasgow, Scotland 7/10-14/2005).