The electronic structures and properties of representative organonitrogen compounds present in crude oil have been calculated using density-functional theory (DFT) under generalized gradient approximation (GGA). These basic and non-basic organonitrogen compounds have distinct electronic structures and properties that determine their HDN reactivities on hydrotreating catalyst surfaces. The HDN reactivities of cyclohexylamines and piperidines can be correlated to the Mulliken charges on the nitrogen atoms of the organonitrogen molecules, and the hydrogenation activities of aromatic molecules can be correlated to the highest occupied pi-orbitals or lowest unoccupied pi-orbitals depending on the electronic structure of the catalyst surface. Adjusting electronic structures of hydrotreating catalysts by insightful incorporation of select promoters will change catalyst HDN selectivity for the hydrotreatment of basic and non-basic nitrogen compounds. (C) 2004 Elsevier B.V. All rights reserved.