Rg1 and Rb1 are two major active compounds of ginseng that facilitate learning and memory. The present study aimed to compare the nootropic effects of Rg1 and Rb1 in a scopolamine induced dementia mice model. After 6 and 12 mg/kg of Rg1 and Rb1 intraperitoneal administration to mice for 7 days, their effects were assessed using the step-down passive avoidance (SD) and the Morris water maze (MWM) tests, the acetylcholinesterase (AChE) activity, acetylcholine (ACh) content and serotonin (5-HT) level in the hippocampus were analysed after SD and MWM tests. The results showed that Rg1 and Rb1 ameliorated cognition-deficiency in mice with dementia. Rg1 showed stronger effects than Rb1 on escape acquisition in MWM. Both Rg1 and Rb1 increased ACh levels in the hippocampus, but Rg1 inhibited AChE activity while Rb1 had no effect on AChE activity. Both Rg1 and Rb1 inhibited the decrease of 5-HT induced by scopolamine, but Rb1 was more active than the same dose of Rg1. These results demonstrate that multiple administrations of Rg1 and Rb1 are effective in improving memory deficiency induced by scopolamine. Rg1 appears to be more potent than Rb1 in improving acquisition impairment, and the two ginsenosides may act through different mechanisms.