Leiomyoma is a benign smooth muscle tumor that may occur throughout the entire digestive tract. It occurs more frequently in the stomach and the small intestine, but is rarely seen in the large intestine. Here, we report two cases of colon leiomyoma mimicking the appearance of colon polyps that were found incidentally. They were simultaneously diagnosed and treated by endoscopic mucosal resection. Careful and thorough endoscopic examination is required for differential diagnosis of polyps that may actually be subepithelial tumors.