Background:  Numerous methods have been developed to resect early-stage gastric and esophageal cancers, but it is difficult to resect lesions viewed tangentially with the endoscope. Methods:  We have designed and developed an original method of endoscopic mucosal resection using a partial transparent hood to treat difficult cases in which the lesions are located tangentially to the endoscope. The hood was attached on the right side of the endoscope and, after insertion into the stomach or the esophagus, was lightly pressed on the orad side of the lesion. Then the lesion was resected using grasping forceps and electrosurgical current snare. Results:  The average diameter of specimens was 26 ± 8 mm in gastric lesions and 20 ± 3 mm in esophageal lesions, both 6 mm larger than those obtained by previous methods. Conclusion:  This device and technique were extremely useful for mucosal resection of lesions located tangentially to the endoscope.