Achalasia and gastroesophageal reflux disease (GERD) are on opposite ends of the spectrum of lower esophageal sphincter dysfunction. Heartburn is the main symptom of GERD. However, heartburn and regurgitation are frequently observed in patients who have achalasia. The diagnosis of achalasia might be delayed because these symptoms are misinterpreted as gastroesophageal reflux. Here, we reviewed the clinical characteristics of patients with the erroneous diagnosis of GERD who actually had untreated achalasia.