This report describes three cases where colonic submucosal tumors (SMT) were definitively diagnosed using endoscopic submucosal dissection (ESD) as excisional biopsy. ［Case 1］ An approximately 8 mm hemispherical SMT with a smooth surface was present in the rectosigmoid colon of a 44-year-old woman. Endoscopic ultrasonography (EUS) showed hypoechogenicity in the third layer from the epithelial lining. ESD was performed, and histopathological examination revealed a leiomyoma. ［Case 2］ A ＜10 mm yellowish hemispherical SMT was present in the ascending colon of a 43-year-old man. An SMT with hyperechogenicity was suspected in a region of calcification, with the main locus assumed to be in the tertiary layer based on EUS findings. A granular cell tumor was diagnosed, and ESD was performed. The histopathological diagnosis was leiomyoma with calcification. ［Case 3］ A 7 mm yellowish SMT with a mildly irregular surface was present in the transverse colon of a 63-year-old man. EUS revealed a hypoechoic spherical mass, assumed to be located in the tertiary layer. The resected specimen showed necrotic nodules in the submucosa. Colonic SMTs are difficult to diagnose in many cases and are simply followed up ; however, ESD as excisional biopsy may aid in diagnosis in such cases.