The cognitive dysfunctions observed in patients after anesthesia are due not only to the effects of but also to the surgery, the disease requiring surgery, and post-operative treatment. Initial cognitive recovery from anesthetic agents is usually fast, from several hours to several days, but can be delayed by postoperative treatment (analgesia, for example) that have deleterious cognitive effects. During the initial period after surgery, acute impairment of cognitive functions is seen in some patients at risk (major surgery, aged patients, brain sensitivity, or sepsis), specifically transitory (1-3 days in most cases) postoperative delirium. This delirium or confusion requires follow-up at 3 months to check cognitive functions, especially in aged patients. Cohort studies show that cognitive impairment can be objectively identified at one week after surgery with general anesthesia in around 40% of patients, regardless of age. This risk is reduced slightly by the use of loco-regional anesthesia. Cognitive dysfunction is still observed at 3 months after surgery in about 10-15% of patients older than 60 years and in about 6% of younger patients. In patients with a pre-existing cerebral disease with cognitive symptoms, the incidence of long-lasting additional cognitive impairment remains unknown. The mechanisms of this long-term cognitive dysfunction remain to be elucidated.