Pinewood particles were pyrolyzed in a vertical tube furnace at 500 degrees C followed by the upgradation of pyrolysis vapors using zeolite ZSM-5 at catalyst temperature from 400 to 600 degrees C. The catalyst was later regenerated to recover its acidity and activity. The bio-oil before catalysis was homogeneous and highly oxygenated, and neither aromatic nor polycyclic aromatic hydrocarbons (PAHs) were detected. The difference in water yield was very small for different catalytic pyrolysis cases, and experimental results indicated that the conversion of oxygen was mainly to CO and CO2 as the catalyst temperature increased. Chemical analysis of the bio-oil showed that aromatic hydrocarbons and PAH were formed in significant amounts upon catalytic treatment. Finally, the content of acids and ketones was reduced after catalysis, showing an improvement in the quality of bio-oil. The overall effect of the usage of regenerated catalyst on the pyrolysis products was not significant in the current study.