Ectopic ACTH syndrome is a rare differential diagnosis of hypokalemic hypertension. Patients with ectopic ACTH syndrome due to small cell lung cancer have a poor prognosis. We report on a 68-year-old female patient who presented with dyspnea and hypokalemic hypertension. Endocrine testing was consistent with ectopic ACTH syndrome due to small cell lung cancer. After initiation of chemotherapy with etoposide and carboplatin ACTH and cortisol levels normalized and clinical symptoms impressively improved.