BACKGROUND: Studies on the circadian variation in bodily functions and sleep are important for understanding the pathophysiological processes in the postoperative period. We aimed to investigate changes in the circadian variation in activity after minimally invasive surgery (laparoscopic cholecystectomy, LC) and major abdominal surgery (MAS) and if these changes correlated with postoperative subjective recovery measures. METHODS: We examined 76 and 44 patients undergoing LC and MAS, respectively, for 4 days before and after surgery. Subjective recovery parameters were assessed by visual analogue scale (sleep quality, general well-being and pain) and fatigue was measured by a ten-point fatigue scale. The activity levels of the patients were monitored by actigraphy (a wrist-worn device measuring patient activity). Measures of circadian activity level [interday stability (IS), intraday variability (IV) and the amplitude (AMP)] were derived after nonparametric analysis of activity data. RESULTS: IS was significantly reduced both after MAS (0.72 before surgery and 0.58 after surgery, p < 0.0001) and after LC (0.76 before surgery and 0.66 after surgery, p < 0.0001). The IS dropped significantly more following MAS surgery compared with following LC surgery (p < 0.001). The fragmentation of the rhythm IV increased and the amplitude dropped significantly after both LC and MAS surgery. Subjective recovery parameters were worse after MAS when compared with LC, and correlated significantly to the circadian activity parameters (IS, IV and AMP). CONCLUSION: Severely disturbed circadian activity parameters was found after both LC and MAS with worse changes after MAS. Measures of circadian activity pattern analyses correlated significantly with postoperative subjective recovery parameters.