The catalytic cracking of a blend of raw bio-oil (20 wt %) from black poplar sawdust fast pyrolysis and vacuum gasoil (VGO, 80 wt %) has been studied. The runs have been performed in a riser simulator reactor (RSR) under fluid catalytic cracking (FCC) conditions; that is, 500-560 degrees C, catalyst to feed mass ratio of 6 g(cat) (g(feed))(-1) on a dry basis, reaction times of 3-10 s and a equilibrated commercial FCC catalyst. The cofeeding effect has been quantified by comparing the yields of product lumps and individual components in the gaseous fraction and gasoline lump in the cracking of VGO, raw bio-oil, and their blend (20% bio-oil/80% VGO), at the same conversion values (60-70 wt %). The cofeeding has a favorable synergy because it promotes the formation of C-3 - C-4 and gasoline (C-5-C-12) hydrocarbon lumps, attenuating the formation of CO2, CO, and also coke formation. In the cracking of the blend (80% VGO/20% bio-oil) at 70 wt % conversion, a deoxygenation degree of 95 wt % has been obtained, with a total liquid fuel yield of 52.8 wt % and a gasoline yield of 31.6 wt %, with a low oxygenate fraction (<4 wt %) containing carboxylic acids, aldehydes, ketones, and phenols.