A device for immobilizing a patient for a medical test or operation includes a molding element that is convertible from a flexible, elastic form to a rigid form by the application of a vacuum. The molding element is attached to the patient by an elastic layer while in the flexible, elastic form where it conforms to the contours of the patients body. Then the molding element is converted to its rigid form thereby immobilizing the patient. Auxiliary devices can be attached to the immobilizing device and these devices, such as a pivot arm suspension can be used to fix the immobilized patient to an operating table.