Endoscopic submucosal dissection (ESD) has become the standard procedure for treatment of early gastric cancer [1]. Few studies have addressed anesthesia or sedation methods during ESD [2-5]. In Yurtlu et al. [2] general anesthesia was compared with propofol based sedation, and in Park et al. [3] intermittent and continuous sedation methods were compared. When sedation is used during ESD, it is usually moderate to deep sedation because of the long procedure time and pain caused by incision, dissection, hemostasis, air insufflation and rotation of the scope [6,7]. However, there are concerns about respiratory complications, such as respiratory depression and aspiration pneumonia when deep sedation is used in ESD [6]. Recently, Yoo et al. [6] reportedthat sedation targeted to light sedation could be an alternative to moderate sedation with a score of 2 or 3 from Modified Observer's Assessment of Alertness/Sedation (Table 1). Light sedation during ESD permits some movement and cooperation from patients. However, this may hinder endoscopists from performing the procedure efficiently and could prolong the procedural time. Therefore, moderate to deep sedation is the generally agreed level of sedation for better procedural condition, which allows the endoscopist to perform ESD with