Abstract This study was designed to passivate vanadium on an ultrastable Y zeolite-based FCC catalyst. The passivating agents are rare-earth compounds soluble in hydrocarbons (dysprosium and samarium naphthenate, lanthanum octoate) which are introduced on the catalyst at the same time as vanadium naphthenate. Adsorption measurements show that more than 90% of the zeolite structure is preserved after high-temperature hydrothermal treatments when La/V = 1. High-resolution analytical microscopy shows that vanadates (SMVO 4, LaVO 4), in the form of small particles, are formed on the surface of the catalyst grains on the matrix and both on the external surface and in the mesopores of the zeolite. The gasoline yield measured with a microactivity cracking test is maintained at a high level, but coke and hydrogen yields remain higher than those on an unpoisoned catalyst.