A rare case of combined unilateral adrenal hyperplasia and paraganglioma is reported. A 27-year-old woman presented with hypertension, palpitation, dizziness, and headache for about 3 months. Elevated plasma aldosterone with low renin and a high level of urine vanillylmandelic acid (VMA) were found. Computed tomography showed a microadenoma of the left adrenal gland and a well demarcated left retroperitoneal para-aortic mass. Adrenal vein sampling for aldosterone and renin levels suggested left adrenal lesion. Surgical removal of the left adrenal gland and para-aortic mass was performed. Pathologic examination of the resected left adrenal gland showed adrenal cortical hyperplasia and the left retroperitoneal para-aortic mass showed a paraganglioma. Postoperatively, blood pressure, plasma renin, aldosterone and urine VMA all returned to within normal ranges. The possible relationship of these two diseases is discussed.