A novel cracking catalyst, a method of preparing same and an improved hydrocarbon cracking process are provided wherein adverse effects of metals such as nickel, vanadium, iron, copper and cobalt in the cracking catalyst are precluded or mitigated by contacting the cracking catalyst with (A) at least one of elemental antimony and compounds thereof and (B) at least one of element tin and compounds thereof whereby there is added to said catalyst a modifying amount of each of (A) and (B) with the weight ratio of antimony to tin being such as to provide passivation of the contaminating metals greater than the sum of the passivation effects of each of (A) and (B) individually. In general the ratio will be in the range of from 0.001:1 to 1000:1, and preferably will be in the range of 0.05:1 to 50:1.