Effective treatment of residue generated from the pyrolysis of polystyrene wastes has been one of the important factors in the recovery of styrene monomer and oil from polystyrene wastes. Depending on the experimental conditions, the yields of oil and styrene monomer are considerably decreased in the presence of residue. Here the residue was decomposed effectively in a catalytic fluidized-bed reactor. Nitrogen and silica sand were used as a fluidizing gas and a bed material, respectively. Effects of catalyst, temperature and gas velocity on the characteristics of decomposition of the residue were examined. It was found that the residue could be decomposed to oil or chemicals effectively by means of a catalytic fluidized-bed reacting system. The yields of oil and individual chemicals and the composition of the products were dependent upon the operating variables such as reaction temperature, catalyst and gas velocity.