The present invention relates to Chimeric Antigen Receptors (CAR) that are recombinant chimeric proteins able to redirect immune cell specificity and reactivity toward selected membrane antigens and more particularly in which extracellular ligand binding is a scFV derivedfrom a CD123 monoclonal antibody conferring specific immunity against CD123 positive cells. The engineered immune cells endowed with such CARs are particularly suited for treating lymphomas and leukemia.