Various papers have shown enhanced olefin yields during steam cracking when a catalytic surface is introduced. Our studies reveal that increased light olefin yields during catalytic steam cracking are mainly due to a surface volume effect and not to a traditional catalytic effect. Augmentation of yields is also observed if inert material is introduced. We showed that this increase in ethene yield is not an artifact of altered radial or axial heat and mass transfer in the reactor arising from the presence of a packed bed. As a result, the surface-to-volume ratio mainly determines the increase in yields with respect to the homogeneous steam-cracking process. The main effects of the potassium-containing catalyst appear to be suppression of coking activity.