The upgrading of wood pyrolysis oils produced in the ENEL fast-pyrolysis plant located in Bastardo, Italy, and in the Union Fenosa fast-pyrolysis plant located in La Coruna, Spain, was studied by using HZSM-5 and H-Y zeolites in a fixed-bed laboratory scale reactor, at different temperatures and residence times. The products of the catalytic upgrading were a liquid fraction, char, coke, tar and gas. While the upgraded liquid obtained by using the HZSM-5 consisted of easily separable organic and aqueous layers, the liquid obtained by using the HY zeolite consisted of a single phase in which the organic components were either dispersed or dissolved in the water. The effect of temperature, catalyst type and residence time in the reactor on the yields of the fractions obtained (oil, char, tar, coke, gas and aqueous fraction) and on the characteristics of the upgraded oils was examined.