In the present work, we have investigated how the single and combined addition of commercial separate particle additives, such as Bottom Cracking additive (BCA) and Propylene Booster additive (ZSM-5 based-PBA), to a FCC USY catalyst can influence the product distribution and quality during FCC processing. Due to the relatively low catalytic activity of the BCA additive, the increasing single addition of BCA implies a higher ratio of thermal to catalytic cracking, leading in particular to higher dry-gases and coke selectivities and a lower gasoline pool quality. The Bottom Cracking ability of the BCA additive is feed dependent and starts to be representative for high addition levels of about 50-60 wt%, allowing the increase of the LCO pool selectivity and quality. The single and low addition level (i.e. 10 wt%) of ZSM-5 based additive allows to drastically improve the light alkenes selectivity at the expense of the gasoline selectivity, improving, due to concentration effects, the quality of the FCC gasoline pool, but generally limiting the LCO selectivity and quality while the coke selectivity is little increased. The combined use of both additives looks like an interesting upgrading strategy considering that it is possible to keep a high catalytic activity, to fully take advantage of the beneficial effects of the ZSM-5 and BCA additives, and to mitigate at the same time the increase of the coke and dry gases selectivities. (C) 2012 Elsevier B.V. All rights reserved.