Biofuels are called upon to play an important role, not only in reducing the associated greenhouse-gases emissions, but also in enabling the gradual independence from fossil sources, rendering low-carbon-highly sustainable fuels. Today, the involvement of biomass-derived sources into existing petroleum refineries has a growing interest due to the increasing unpredictability of oil prices, environmental concerns and the necessity to secure an energy supply. Petroleum refineries already have a well-developed infrastructure to produce fuels and base chemicals and, consequently, would not require additional intensive investments for processing of alternative feedstocks. From this point of view, co-processing of biomass-derived feedstocks with petroleum fractions is an attractive option, which has already been industrially demonstrated in some cases. There are two main technologies that could be used for co-processing of biomass feedstocks with petroleum fractions, the first one being catalytic hydroprocessing and the second one being fluid catalytic cracking (FCC). Both technologies are found in virtually any conventional refinery. It is obvious that the co-processing of biomass-based feedstocks with petroleum fractions has the potential to play an important role in the near future. There are several research studies in literature that examine both technologies for co-processing. However, while there are many technological reviews that focus on stand-alone biofuel production (e.g., FAME biodiesel, bioethanol, HVO etc.), a dedicated technological review on co-processing for production of hybrid fuels is still missing. Therefore, this paper is focused on presenting a state-of-the-art review on co-processing bio-based feedstocks with petroleum fractions via hydroprocessing and fluid catalytic cracking, looking at different potential feedstocks, catalysts, operating conditions, products and benefits in detail. As there is no specifically dedicated literature review in this field, the content of this review provides a guideline on co-processing of different bio-based feedstocks with petroleum fractions, aimed at delivering a technological assessment of the existing research efforts. (C) 2018 Elsevier Ltd. All rights reserved.