Postoperative delirium is a frequent complication after cardiac surgery. In the literature an incidence ranging from 0 - 72 % is reported. The aetiology of this complication is multifactorial. A decline in cerebral cholinergic transmission as well as perioperative cerebral hypoperfusion or a systemic inflammatory response triggered by the extracorporeal circulation have been suspected. Advanced age is the most important patient-related risk factor. A perioperative delirium is an extremely unpleasant experience for the affected patients. Equally important is the fact that a delirium is associated with a prolonged length of stay on the intensive care unit and in hospital. Furthermore, patients who develop delirium have an increased six-month mortality. Recently successful treatment and prevention of the delirium with cholinesterase inhibitors such as rivastigmine have been reported.