Addition of polyethylene glycol (PEG) as a water soluble organic compound to the impregnation solution during catalyst preparation was investigated to improve NiO _ MoO3/Al2O3 and NiO _ MoO3 _ P2O5/Al2O3 hydrodesulfurization catalysts. XPS measurement suggested that PEG addition increases the dispersion of nickel and molybdenum on the alumina support and improves dibenzothiophene and resid hydrodesulfurization activity. The effect of PEG addition was significant for catalyst prepared from alumina with lower specific surface area and higher phosphorus content, in which the active metal precursor tends to easily aggregate. PEG might block the aggregation of active metal precursors during the drying step and may increase the number of hydrodesulfurization active sites.