Abstract: The invention is relative to monoclonal anti-CD123 antibodies, or fragments thereof that specifically bind to the alpha chain of the human interleukin 3 (IL3) receptor. Further, the invention is relative to an isolated nucleic acid molecule encoding a chimeric antigen receptor (CAR), wherein the CAR comprises an antibody or an antibody fragment which includes an anti-CD123 binding domain, a transmembrane domain, and an intracellular signaling domain comprising at least a stimulatory domain, polypeptides encoded by said nucleic acid molecule as well as an isolated chimeric antigen receptor (CAR) molecules comprising such an antibody or antibody fragment. The invention is also relative to a vector comprising a nucleic acid molecule encoding a CAR, as well as a T cell comprising said vector, and to the use of a T cell expressing a CAR molecule for a treatment of a proliferative disease in a mammal, such as cancer.