Pyrolysis of polystyrene waste foams with or without catalyst was investigated. Waste packaging polystyrene foams, densified by heating in an oven at 125 degrees C, were pyrolyzed at a semi-batch reactor that has specially designed thermal and catalytic parts. The effects of temperature and catalyst type on pyrolysis products and their product distribution were examined. The experiments were carried out at a temperature ranging from 400-500 degrees C. Ni, Cu, Ce, Co, and La with gamma-Al2O3 support were synthesized as catalysts. The highest conversion in catalytic pyrolysis was obtained with Cu/gamma-Al2O3 catalyst. The components of the liquid are mainly styrene monomer, ethylbenzene, toluene, alpha-methylstyrene, and 1,3-diphenylpropane. At 500 degrees C the highest styrene yields were obtained with Cu/gamma-Al2O3 and thermal run. These yields are 63.59 and 63.55%, respectively.