Objectives : The purpose of this study was to characterize the effect of the fraction of Taraxacum officinale and T.coreanum on the learning and memory impairments induced by scopolamine. Methods : The cognition-enhancing effect of Taraxacum officinale and T.coreanum was investigated using a passive avoidance test, the Morris water maze test and Y-maze test in mice. Drug-induced amnesia was induced by treating animals with scopolamine (1 mg/kg, i.p.). Results : The results showed that the Aug harvested T.offiicinale extract-treated group (200 mg/kg, p.o.) and the tacrine-treated group (10 mg/kg, p.o.) significantly ameliorated scopolamine-induced amnesia based on the Passive avoidance Y-maze test and Watermaze test. And these results are same manner in DPPH radical scavenger effect and Acetylcholineseterase inhibition effect. Conclusions : These results suggest that Taraxacum officinale extract maybe a useful cognitive impairment treatment, and its beneficial effects are depending on the collecting time and origin plants. As a result, Taraxacum officinale harvested in August improve memory most.