The catalytic pyrolysis of gas oils and heavy oils over catalyst CEP-1 was investigated in a confined fluidized bed reactor. The influence of feed properties and reaction conditions on product yield and distribution was studied. A feed property parameter (P(FP)) is proposed to characterize the pyrolysis performance of gas oils and heavy oils. The pyrolysis performance of the feed is considered desirable for P(FP) above 15, and undesirable for P(FP) below 10. A reaction extent function (F(s)) dependent on the reaction temperature, residence time and weight ratios of catalyst-to-oil and steam-to-oil is also proposed to describe the reaction conditions of catalytic pyrolysis. A correlation model is established to predict the product yield of catalytic pyrolysis of gas oils and heavy oils on the basis Of P(FP) and F(s). The correlation coefficients were estimated by least square regression analysis of the experimental data. The correlation model shows good calculation accuracy. (C) 2008 Elsevier Ltd. All rights reserved.