The degree of deactivation was studied on the hydrotreating catalyst by using four different feed stocks. This work demonstrated that the deactivation by metals in resin and asphaltene parts of the heavy crude oil and residues was different. The degree of deactivation by metals does not always depend on the concentration of these, but also the nature of the metals. Firstly, the metals in resin part may not have as adverse effect on deactivation as the metals in asphaltene part have. It may possible that these metals in resin may deposit on the bare alumina surface, not on the active sites. Secondly, the nickel containing compounds in the feed deactivate the HDS active sites in lesser extent than that done by vanadium compounds. The deactivation by heavy crude having high concentration of wax materials suggests that long paraffinic or naphthene/aromatic substituted paraffinic chains may take part in coke formation during hydroprocessing reaction conditions. This coke mostly covers the HDS active sites of the catalyst; but does not precipitate as solid coke. The formation of solid coke is observed for the feeds having high percentage of asphaltene content. (C) 2016 Elsevier Ltd. All rights reserved.