Objective: Different anaesthetists for sedation or monitored anaesthesia care have been used for colonoscopy. The target of this research was the ability to perform colonoscopy under a painless degree of sedation and the prevalence of undesired proceedings. Methods: A total of 60 patients were randomly divided into two groups: Group D received dexmedetomidine and Group PF received propofol-fentanyl. Patients in both groups received the same infusion ratio. The minimum infusion amount of dexmetatomidine is (0.1 to 0.4 mu g kg -1 h -1 ) in Group D, whereas fentanyl is administered at a rate of 0.01 to 0.05 mu g kg -1 min -1 in the PF group during the approximately 45 -min colonoscopy. Results: Group D exhibited significantly lower modified Observer's Assessment of Alertness/Sedation (OAA/S) scores at intraoperative time points T1 -T12. Group D also exhibited significantly lower visual analog scale scores for pain at intraoperative time points T4 and T7. The mean arterial pressure was significantly lower in Group D at intraoperative times T6 -T8 and T11 -T12, as well as upon admission to the post -anaesthesia care unit (PACU) and 30 min after admission to the PACU. The results of the ANOVA tests revealed a significantly lower heart rate in Group D. The respiratory rate exhibited a notable decrease during time intervals T8 and T10 in the PF group. Conclusion: The administration of dexmetatomidine and propofol-fentanyl during colonoscopy was found to be safe. In addition, dexmetatomidine may present significant benefits in this context because of its lower occurrence of adverse respiratory events.