Cognitive dysfunction is a frequent complication after cardiac surgery and has been found to be associated with decreases in cerebral oxygen saturation measured with near-infrared spectroscopy. Sevoflurane has neuroprotective properties in vitro and in animal models. This study was designed to determine cognitive and clinical outcomes after sevoflurane- compared with propofol-based anaesthesia for on-pump cardiac surgery and the impact of decreases in under different anaesthesia regimens. Methods. One hundred and twenty-eight patients were randomly assigned to either i.v. anaesthesia with propofol- (PROP) or sevoflurane-based anaesthesia (SEVO). An intraoperative was defined as desaturation. The Abbreviated Mental Test, Stroop Test, Trail-Making Test, Word Lists, and mood-assessment tests were performed before, 2, 4, and 6 days after cardiac surgery. Markers of general outcome were obtained. Results. The analysis groups had differences in baseline cognitive performance. Analysis of variance for repeated measures (incorporating covariance of baseline scores) showed that in three of four cognitive tests, patients with cerebral desaturation showed worse results than patients without desaturation. Patients assigned to sevoflurane-based anaesthesia showed better results in all cognitive tests than patients after propofol. Interactions between the anaesthetic regimen and desaturation were found in all four cognitive tests. There were no differences in markers of organ dysfunction or general clinical outcome. Conclusion. sPatients with impaired cognitive performance before operation may be at particular risk for intraoperative cerebral insult. A sevoflurane-based anaesthesia was associated with better short-term postoperative cognitive performance than propofol.