More than 20% of patients of 65 years or older may develop a delirium after cardiac surgery. Patients with delirium frequently show a disturbed 24-hr motor activity pattern, but objective and quantitative data are scarce. Our aim was to quantify motor activity patterns in elderly patients with or without a postcardiotomy delirium after elective cardiac surgery. Wrist-actigraphy was used to quantify 24-hr motor activity patterns for a 5-day period following cardiac surgery in 79 patients of 65 years or older. Clinical state was monitored daily by means of the Confusion Assessment Method-Intensive Care Unit and the Delirium Rating Scale-Revised 98. The activity Amplitude, and the daytime Activity/minute and Restlessness index were significantly higher and the daytime number of Immobility minutes significantly lower for the patients without delirium or with short delirium episodes, as compared to patients with a sustained delirium (> 3 days). Actigraphy proves to be a valuable instrument for evaluating motor activity patterns in relation to clinical state in patients with a postcardiotomy delirium.