We report a case of adrenal pseudocyst difficult to differentiate from pheochromocytoma. A right adrenal mass was found in a 41-year-old man after a traffic accident. Plasma level of renin was low, plasma level of aldosterone, and urine levels of aldosterone and catecholamines were high. Dynamic tests for primary aldosteronism and pheochromocytoma were negative. No abnormal uptake was shown in 131I-adosterol or 131I-MIBG scintigram. Adrenal venous sampling presented high levels of catecholamines. Laparoscopic adrenalectomy was performed. Histological examination revealed a pseudocyst with a thick fibrocollagenous wall. We discuss the mechanism of high catecholamine levels in the right adrenal vein.