Citalopram, a selective serotonin reuptake inhibitor (SSRI), is one of the most widely used antidepressants. Recently, citalopram has been reported to improve working memory in patients with depression, and psychotic symptoms and behavioral disturbances in patients with dementia. However, the possibility of using citalopram in the treatment of cognitive disorders has not received much attention. The present study investigated the effects of citalopram on scopolamine- and Delta9-tetrahydrocannabinol (THC)-induced impairment of spatial memory using an eight-arm radial maze and electroconvulsive shock (ECS)-induced immobilization (a behavioral model for the disturbance of consciousness). Low dose citalopram reversed both scopolamine- and THC-induced impairment of spatial memory, suppressed ECS-induced immobilization reversed the THC-induced decrease of acetylcholine (ACh) release in the dorsal hippocampus in vivo microdialysis, and enhanced tremors induced by oxotremorine, a muscarinic M1 receptor agonist. Taken together these findings suggest that low dose citalopram is useful for the treatment of memory deficits and consciousness disturbance.