Abstract: A process for the production of a middle distillate fraction comprising contacting a hydrocarbon feedstock at middle distillate production conditions with a catalyst composition comprising a first modified Y zeolite component and a second modified Y zeolite component in admixture with a refractory inorganic oxide matrix and hydrogenation metals. The first and second modified Y zeolites have an average unit cell size within the range of about 24.20 to 24.85 A and have a difference between their respective average unit cell sizes of at least 0.1 A.