Introduction: Congenital absence of the pericardium is rare cardiac defect with a wide spectrum of clinical presentation. We present a case of partial congenital absence of the pericardium that diagnosed with cardiac CT angio and suggested left phrenic nerve injury during operation. Case: A 58 year-old women with no past medical history was admitted to the cardiology department complaining of frequent resting angina. She had a history of chest trauma, a left rib fracture that occurred in a traffi c accident 2 years previously. Physical examinations were normal. ECG Showed 49beats/minute sinus bradycardia, V1~V4 T wave inversion. Chest radiograph showed normal. Laboratory investigations revealed mild leukocytosis(10. 41*109/L). Echocardiography showed abnormal wall motion of focal mid RV free wall associated with extracardiac compression. (figure 1A,1B) Congenital absence of the pericardium was confi rmed by chest CT angio. (figure 2A, 2B) Coronary angiography was normal. We decided to perform partial pericardial resection. (figure 3) Postoperative chest X-ray fi ndings revealed elevated left diaphragm. (figure 4A, 4B, 4C) We suggested left phrenic nerve injury during operation. But the patient had no associated symptom. Follow-up transthoracic echocardiography was done and the wall motion abnormalities and external compression which were observed in previous study were no longer seen. We decided outpatient department follow-up and the patient was discharged on the six postoperative days with symptom free state. Discussion: The prevalence of congenital absence of the pericardium, including cases with other congenital cardiopulmonary anomalies, has been described as only 0. 002- 0. 044% of surgical/pathologic investigations. All types of congenital pericardial defect can lead to serious complications such as incarceration of cardiac tissue, myocardial ischemia, aortic dissection or valvular insuffi ciency. Phrenic nerve injury was observed from 0. 5% to 1. 7% undergoing closed cardiac procedures. In general, these injuries gradually resolve spontaneously over time.