Achalasia is an esophageal motility disorder that is accepted as a risk factor for the development of cancer. Especially in megaesophagus, chronic irritation of foods and bacterial overgrowth may contribute to the formation of high-grade dysplasia and squamous cell carcinoma. We present a case of advanced stage achalasia with high-grade dysplasia detected three years after a cardiomyotomy operation. Cancer risk continues after surgical operation in achalasia, like in this case. In conclusion, endoscopic follow up is necessary for these patients even after surgical treatment.