The present invention is concerned isoxazole-imidazole derivatives having affinity and selectivity for GABA A α5 receptor binding site, their manufacture, pharmaceutical compositions containing them and their use for enhancing cognition or for the treatment of cognitive disorders like Alzheimer's disease. In particular, the present invention is concerned with aryl-isoxazol-4-yl-imidazole derivatives of formula I wherein R1, R2 and R3 are as described in the specification.