This study presents a detailed analysis of the catalytic de-oxygenation of the liquid and gaseous pyrolytic products of two biomasses (beech wood and flax shives) using different catalysts (commercial HZSM-5 and H-Y, and lab-synthesised Fe-HZSM-5, Fe-H-Y, Pt/Al2O3 and CoMo/Al2O3 ) . The experiments were all conducted in a semi-batch reactor under the same operating conditions for all feed materials. BET specific surface area, BJH pore size distribution and FT-IR technologies have been used to characterise the catalysts, while gas chromatography-mass spectrometry ( GC-MS ) , flame ionisation detection ( GC-FID ) and thermal conductivity detection ( GC-TCD) were used to examine the liquid and gaseous pyrolytic products. It was firstly seen that at higher catalyst-to-biomass ratios of 4:1, de-oxygenation efficiency did not experience any further significant improvement. Fe-HZSM-5 was deemed to be the most efficient of the catalysts utilised as it helped reach the lowest oxygen contents in the bio-oils samples and the second best was HZSM-5. It was also found that HZSM-5 and H-Y tended to privilege the decarbonylation route ( production of CO ) , whilst their iron-modified counterparts favoured the decarboxylation one ( production of CO2 ) for both biomasses studied. It was then seen that the major bio-oil components ( carboxylic acids) underwent almost complete conversion under catalytic treatment to produce mostly unoxygenated aromatic compounds, phenols and gases like CO and CO2 . Finally, phenols were seen to be the family most significantly formed from the actions of all catalysts.