The conversions and yields of the fractions of gases (C-1, C-2) LPG (C-3, C-4), gasoline (C-5-C-12), and coke and their compositions have been studied in the catalytic cracking of blends made up of polystyrene and polystyrene-butadiene with a LCO (light cycle oil, which is a secondary refinery product) used as the solvent. The catalysts were prepared from HZSM-5 zeolites of different total acidities. The reaction was carried out in the 450-550 degreesC range and under the standard conditions of FCC units. The important effects both of the total acidity of the zeolite and of the temperature on the conversion and yield of styrene are demonstrated. Total recovery of the monomer styrene is attained at 550 degreesC. Likewise, the LCO is valorized, as high yields of both the C-5-C-12 aromatic fraction and LPG (olefinic) are obtained with low yields of gases (C-1, C-2) and coke.