The effect of different aromatic diluents on sediment formation during the catalytic hydrotreating of heavy crude oil was studied. The experiments were carried out using a heavy crude oil with 11.69 degrees API and three aromatic streams from an industrial Fluid Cracking Catalytic plant: light cycle oil, heavy cycle oil, and decanted oil. All tests were performed in a batch reactor at reaction time of 2-4 h, reaction temperature of 380-420 degrees C, and addition of aromatic diluents in 5 and 10 wt % with respect to the crude oil. The reaction pressure and stirring rate were kept constant at 100 kg/cm(2) and 1000 rpm, respectively. The results of the hydrotreating tests showed that the amount of sediment increases as the time and reaction temperature do, being the temperature the variable that has the greatest effect on sediment formation. Light cycle oil provides a greater suppression of sediments. This effect was attributed td the greater amount of total aromatic compounds (mainly diaromatics) able to keep asphaltenes solvated.