With the increasing amount of shale oil in the worldwide market it becomes necessary to analyze, from the refinery point of view, what is the real impact of processing shale oil derived feeds on the catalytic system of hydrotreating units. Compared with conventional oil, shale oil normally has higher content of contaminants like Arsenic (As), Vanadium (V), Nickel (Ni) and Silicon (Si). All those contaminants need to be trapped before entering the main catalyst bed were the Hydrodesulfuration (HDS) and Hydrodenitrogenation (HDN) take place. Particularly As is one of the most poisonous metals for hydrotreating catalyst, producing an activity loss of 30% with only 0.5 wt. % accumulation in the catalyst bed. This means that the grading or guard system of a hydrotreating reactor will have a more important role trapping all the contaminants, maintaining as high as possible the main catalyst activity. Another challenge that faced when processing these types of feed is changing the perception of "the normal operation"of the unit. Shale oil contents different components like oxygen, chloride and different properties such as higher bromine numbers that can change dramatically the optimal operating point that the unit usually has. An easy example is the higher bromine number that generates much more exotherm in the reactor that needs to be controlled by quench or by changing the loading scheme. A more complex example could be the presence of oxygen that includes a new reaction that normally is discarded in the hydrotreating studies. In this case the organic oxygen will react mainly by Hydrodeoxygenation (HDO) to form water and also by Hydrodecarboxylation (HDCo) to form CO2 The paper it concludes that more attention is needed in the analysis of the contaminants and general properties of the feed in order to make the best selection of the catalyst. The main challenge optimizing the operation of the unit processing shale oil derives is to take into account the higher amount of nitrogen, olefins and the presence of oxygen. . Since the main reaction related to oxygen will be HDO, the presence of water will be the main factor to deal in the new reactor scheme, normally by treating it with a special layer at the top of the reactor. Another effect of the presence of oxygen is an increase of yields towards light products, since removing the oxygen from the molecule reduces significantly its boiling point. An example of this is the phenol (b.p. 182°C) that would produce benzene with 78°C. The optimal selection of the catalyst system for this type of feeds will derived in a longer cycle length of the unit and a more stable operation.