Fluid Catalytic Cracking is one of the most important processes in the petroleum refinery operations because it produces more valuable products per barrel of feed than other refinery processes. The FCC unit can process any type of crude oil fraction, from light to heavy molecular weight hydrocarbons, with different concentrations of contaminants: S, N, Na, Ni, V, Fe, Mg, K, Ca, resins, and asphalthenes. The yields and quality of the major products depend upon the chemical composition of the feedstock thus influencing the entire refinery economics. To design the FCC catalyst for each type of FCC feedstock composition based upon varying unit operating conditions and constraints is a very difficult issue. The main objective is to achieve the maximum potential valuable products in the commercial unit, which depends on the optimal interaction of feedstock composition and catalyst design. Three major parameters of the catalyst have to be considered in the catalyst design: activity, stability and selectivity. The catalyst activity is related with the amount of active components present in the catalyst formulation: zeolite type and concentration, matrix active components and Re2O3. Catalyst stability is related to the catalyst’s capacity to resist the unit deactivation severity especially in the regenerator, while selectivity is the capacity of the catalyst to maximize the valuables products yields while achieving the FCC unit objectives. To optimize catalyst selectivity it is important to consider the zeolite type and amount, the acid site concentration including site distribution and strength, the zeolite and matrix pore size distributions, the matrix type and activity, the amount of Re2O3 and the presence of additives. This paper describes the effect of the major catalyst components on the activity and selectivity for the most valuable products yields (C4=, LPG, gasoline and coke). At the same time, the analysis considers the maximum feed potential yields and the correlation with the equilibrium catalyst (Ecat) performance. The Ecat performance of different catalysts was studied in the ACE unit at standard conditions, where the maximum feed potential yields are taken as the target for each Ecat sample. To select the best catalyst for the commercial unit it is necessary to include the catalyst stability and the coke selectivity concept, which means the effect of the catalyst in the heat balance. All of these concepts are considered in this paper.