Endoscopic mucosal resection (EMR) is a minimally invasive technique for effective treatment of early stage colorectal lesions with no invasive potential. However, the high frequency of local recurrence after piecemeal EMR for large lesions is considered a serious problem. In contrast, endoscopic submucosal dissection (ESD) allows en-bloc resection, irrespective of the lesion’s size. ESD has been established as a standard method for the endoscopic removal of early cancers in the upper gastrointestinal tract in Japan. Although the use of ESD for colorectal lesions has been studied clinically, ESD is not yet established as a standard therapeutic method. We define the indications for en-bloc resection, based on extensive clinicopathological analyses, as a laterally spreading tumor (LST) non-granular type (LST-NG) lesion greater than 20mm and an LST granular (LST-G) type lesion greater than 40mm. Both of these lesions had a high submucosal invasion rate. Especially, LST-NG type lesions greater than 20mm are technically difficult to remove completely even by piecemeal EMR and are considered a “definite indication for en-bloc resection”. The ESD procedure is undoubtedly an ideal method to achieve en-bloc resection, however, the prevalences of suitable lesions among all neoplastic lesions and among all early cancers were not high (1.0% and 5.0%, respectively). Therefore, it is crucial to master more fundamental therapeutic techniques and have knowledge of surveillance strategy after endoscopic treatment.