Postoperative aneurysms of the right ventricle after correction of Tetralogy of Fallot are usually the consequence of a long standing pulmonary regurgitation or distal pulmonary obstruction. They occur more frequently in patients where a transannular incision has been initially applied. The aneurysm formation is usually slow with progressive dilatation of the anterior free wall of the right ventricle. We report a very early and unusual postoperative polytetrafluorethylene (PTFE) patch aneurysm accidentally discovered in the sixth postoperative week during the prolonged hospital stay due to a postoperative cerebral stroke. The dilatation of the right ventricular outflow tract could not be completely outlined by ultrasound, and Multiple Detector Computed Tomography scan (MDCT) gave an excellent insight to the anatomy of the aneurysm and provided the cardiac surgeon with necessary information. The patch had not been previously resterilized or damaged in any way. The explanted patch was not infected. PTFE aneurysms have been observed and studied for decades and were mostly related to PTFE grafts in vascular surgery. Creep or "cold flow" theories have been proposed to explain gradual stretching of the material, one of them including wall tensions dependent on the pressure and radius parameters.