Pheochromocytoma and paraganglioma are rarely seen cathecolamine-secreting neuroendocrine tumors. We reported a retroperitoneal tumor with a diameter of 5 cm in a 71 years old man. After admission, he was found loss of consciousness suddenly. Myocarditis related to pheochromocytoma was the most possible reason of sudden collapse. The diagnosis of paraganglioma was made later in ICU (intensive care unit). Pheochromocytoma or paraganglioma may present with life-threatening cardiovascular manifestations, such as acute myocarditis, myocardial infarction, and hypertensive emergency. It should never been neglected in the differential diagnosis of retroperitoneal mass lesions.