In this study, we compared ex-situ catalytic pyrolysis (CP) and in-situ CP of hybrid poplar in a micro-reactor system. When both pyrolysis and catalysis were performed at 700 degrees C, the carbon yield of olefins was greater for ex-situ CP than for in-situ CP (17.4% vs. 5.4%). On the other hand, in-situ CP produced more aromatic hydrocarbons than ex-situ CP (26.1% vs. 18.9%). The remarkably high yield of olefins from ex-situ CP indicates the potential of exploiting the process to preferentially produce olefins as a primary product from biomass, with aromatics being the secondary products. The carbon yield of carbonaceous residues from ex-situ CP was 18.6% compared to 31.3% for in-situ CP. Substantial carbon was deposited as char during ex-situ CP, which could be easily recovered as by-product, simplifying catalyst regeneration. The effects of catalyst loading, pyrolysis temperature and catalysis temperature on product distributions for ex-situ CP were also investigated. Our results showed that catalyst temperature strongly affected product distribution. While high catalyst temperature enhanced both olefin and aromatic production, yield of olefin increased to a greater extent than did aromatics. Neither pyrolysis temperature nor catalyst loadings had significant effect on product distribution for ex-situ CP. (C) 2014 Elsevier Ltd. All rights reserved.