Six new N-11C-labeled aminophenylbenzothiazoles substituted with fluorine in different positions have been synthesized and evaluated as amyloid-beta binding ligands. Our structure-property relationship studies show that the substitution pattern of the phenyl ring and the benzothiazole moiety has an influence on the metabolic stability, which in turn has an effect on the brain uptake kinetics. Two lead compounds have been identified with improved physicochemical characteristics for Abeta-plaque imaging in vivo.