Purpose: Several studies of an endoscopic mucosal resection(EMR) have been reported, but reports about benign protruding lesions that arise at the scar of EMR for early gastric cancer (EGC) or a gastric adenoma are rare. The purpose of this study was to elucidate endoscopic and histological characteristics of benign protruding lesions which arise at the scar of an EMR for EGC and a gastric flat adenoma. Materials and Methods: In 101 lesions (73 gastric flat adenomas and 28 EGCs) from 96 patients, 16 lesions developed new protruding lesions that arose at the scar of the EMR. We retrospectively analyzed the endoscopic findings of initial and protruding lesions, and several other clinical factors (H. pylori infection, eradication therapy, and proton pump inhibitor (PPI) or H2-blocker use). Results: 1. The mean duration until detection of the protruding lesion was 8.9 months ($1.5∼27$). Protruding lesions arose at the scar of the EMR in 1 of 28 EGCs ($3.6\%$) and from 15 of 73 gastric flat adenomas ($20.5\%$). All of the patients were men. 2. With respect to the endoscopic findings, the shapes of the protruding lesions were as follows: 10 Yamada (Y) I, 4 Y-II, 1 Y-III, and 1 flat lesion. Histological examination of the protruding lesions revealed regenerating hyperplasia in 5 lesions, intestinal metaplasia in 5, and both in 6. 3. The incidence of these lesions was higher in cases of tubular adenomas with focal high-grade dysplasia than in cases of tubular adenomas without dysplasia (p<0.05). 4. The incidence of H. pylori infection was higher in patients ($81.7\%$) who developed a protruding lesion than in those ($51.8\%$) who did not develop (p=0.029); also, the incidence of use of PPI was higher in those patients (p=0.045). However, eradication therapy for H. pylori and duration of use of PPI or H2-blocker showed no difference between groups. Conclusions: It may be possible that the potential hyperplasia that may reside in normal mucosa surrounding EGC or a gastric adenoma might awaken during the healing process of the EMR ulcer and develop to benign protruding lesions. And, H. pylori and PPI might also be related to the development of the protruding lesions.