A potential valorization pathway for pyrolysis oils from lignocellulosic biomass is their co-hydrotreatment with petroleum cuts to produce transportation fuels. The study of simultaneous hydrodeoxygenation (HDO) and hydrodesulfurization (HDS) reactions is therefore essential before considering such a co-treatment. The influence of different oxygenated compounds on the hydrotreatment of a straight-run gas oil was studied on a CoMo/gamma-Al2O3 catalyst and under industrial operating conditions. The selected compounds were 2-propanol, cyclopentanone, anisole, guaiacol, propanoic acid, and ethyldecanoate, which are representative of the oxygenated chemical families present in bio-oils. Reaction schemes of HDO reactions were proposed for each studied oxygenated compound, and their impact on the gas oil HDS, hydrodenitrogenation (HDN), and aromatic ring hydrogenation (HDCA) was determined. Under our operating conditions, 2-propanol, cyclopentanone, anisole, and guaiacol were not found to be inhibitors of catalytic performances. On the contrary, propanoic acid and ethyldecanoate had an inhibiting effect on HDS, HDN, and HDCA reactions. This inhibition is attributed to a competition between the HDS reactions and the methanation of CO and CO2 formed during the decomposition of ethers and acids. The impact on HDS conversion of dibenzothiophenic compounds was also studied, showing no differences of the inhibiting effect between these molecules.