In this work the effect of active metals, promoters, phosphorous and lithium on hydroprocessing reactions of Maya heavy crude was studied. Four reactions (hydrodemetallization (HDM), hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and asphaltene conversion (HDAsp)) were carried out on seven different catalysts. The support of these catalysts was prepared by urea hydrolysis method. Temperature programmed reduction (TPR) results showed that more reducible species were present on cobalt promoted catalyst compared with unpromoted one. We observed that active metal was more dispersed on P containing catalyst. The conversions, determined as Time Weighted Mean Conversion (TWMC), were very high for a PCoMo catalyst, however, it exhibited a rapid fall of activation. A linear correlation was found between the loss of specific surface area (SSA) and coke formation. The catalysts deactivation was mainly due to coke formation over catalyst surface. Cobalt promoted catalysts showed higher initial HDM conversion compared with Ni one. Mo active metal was better for HDM reaction. Even though lithium-doped catalyst showed slightly higher activities it had no effect on catalyst life. (C) 2003 Elsevier B.V. All rights reserved.