The shale oils of oil shales from Mongolian Khoot, Tesegtiin honhor, Uvurjargalant and Zuun bulag deposits, as well as their distillates were studied by the hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodeoxygenation (HDO) processes for the possibility of improving the quality of liquid products. Elemental and chemical compositions of the shale oils, distillates and hydrotreated oils were examined qualitatively and quantitatively, using a Thermo Scientific FLASH2000 CHNS analyzer and an Agilent 6890A gas chromatograph (GC). Hydrotreatment of Khoot shale oil (KH) under different reaction conditions showed that with increasing reaction temperature from 330 to 370 degrees C, HDN, HDS and HDO increased from 13 to 37%, from 65 to 92% and from 59 to 81%, respectively. Among the shale oils hydrotreated at a temperature of 350 degrees C for 2h, the Uvurjargalant shale oil (UJ) had the highest conversion by HDN (39%), HDS (89%) and HDO (71%).