Neuropsychological and neuropsychiatric disorders following open heart surgery are estimated to occur in as many as 80 per cent of all patients. They have been recognised from the very beginning of modern heart surgery. Despite a huge amount of scientific literature, data concerning incidence, the phenomenology and duration of symptoms diverge. This finding may be explained by heterogeneous aetiopathogenetic concepts and methodological and terminological problems associated with the investigation of postoperative delirium or neuropsychological and psychopathological sequelae of cardiac surgery. Nowadays, most authors agree in respect of a multifactorial pathogenesis of cognitive deficits following cardiac surgery. Factors influencing the psychopathological and neuropsychological outcome of cardiac surgery can be divided into pre-, intra- and postoperative variables. Advanced age, degree of cardiovascular impairment and other case histories, as well as history of drug abuse, are those preoperative variables that may be responsible for a postoperative cognitive decline. The predictive value of personality traits (depression and/or anxiety), however, is most controversial. Among the intraoperative variables related to the postoperative cognitive state, are e.g. the type of operation and technical procedure (micro-/macroembolism due to the way of oxygenation, pulsatile/-non-pulsatile flow) and duration of extracorporeal circulation. In the postoperative period, the duration of intubation or ICU stay and related variables (like sleep or sensory deprivation/hyperstimulation) were identified as significant predictors of neuropsychological and psychopathological alterations. Modern research focusses on neurobiochemical markers of brain injury which may serve as early predictors of a postoperative cognitive decrease. These parameters may indicate an early postoperative diagnosis and neuroprotective treatment in patients at risk.