Untreated and mildly hydrotreated pyrolysis derived liquids are evaluated in FCC processing by co-feeding with vacuum gas oil ('VGO'). Pyrolysis liquids (PLs) applied are from the Empyro plant in the Netherlands. The treated PLs are produced by BTG employing novel bimetallic Ni-based catalyst (Picula), at 200 bar hydrogen pressure and two temperatures, 120 degrees C and 225 degrees C. A pilot scale riser setup (riser: I.D. = 7 mm, length = 9 m; combustor: I.D. = 78 mm) is employed to process the liquids with VGO. The riser is operated at a riser outlet temperature of 525 degrees C, atmospheric pressures and Cat-to-Oil ('C/O') ratio ranging from 5 to 8. Co-processing ratios are kept constant at 10:90 (PLs:VGO). The most relevant observations compared to processing of only VGO are: - At all C/O ratios, the conversion observed in the co-processing tests is higher. - The yield of coke, dry gas and LPG in all co-processing tests is lower. - At such high substitution levels co-processing crude PL shows a decrease in the gasoline yield and slightly higher yield of LCO and bottoms. - The treated bio-liquids yield similar levels of gasoline and LCO. During crude PL co-processing CO and CO2 are noted, and a decrease in H-2 yield is found compared to pure VGO. Renewable carbon is observed in the liquids obtained in both co-processing crude PL and stable pyrolysis oil (SPO), while the mild hydrotreating steps are more effective.