Background and Aims:Sedation in paediatric cancer for fractionated radiation treatment (RT) is unique as the child has to be still for accurate delivery of RT, monitoring of the child is from a remote location and sedation is repeated for multiple sessions of RT. The present study was undertaken to compare the efficacy of intranasal dexmedetomidine with oral midazolam and ketamine combination for repeated sedation during fractionated RT in paediatric oncology.Methods:Ninety children aged between 3-6 years, planned for 21 fractions of RT, were randomised to receive intranasal dexmedetomidine 2 mg/kg (group D) or oral midazolam 0.2 mg/kg and ketamine 5 mg/kg (group MK). The 21 sessions of fractionated radiotherapy were divided into three subgroups of seven consecutive exposures 1–7, 8–14 and 15–21 for comparison. The primary endpoint was to determine the incidence of successful sedation. The sedation score achieved, time to satisfactory sedation and discharge, rescue ketamine required, and side effects were secondary endpoints.Results:The incidence of successful sedation in the three successive RT subgroups; sessions: 1–7, 8–14 and 15–21, was 82%, 75.6% and 66.7% in group D, as compared to 40%, 24.4% and 13.3% in group MK, respectively. (P < 0.001). A decrease in successful sedation was noted in the successive subgroups. Time to successful sedation and discharge was earlier in group D in comparison to MK (P = 0.000). More patients in group MK required rescue ketamine (P = 000).Conclusion:Intranasal dexmedetomidine produces more satisfactory sedation as compared to oral ketamine with midazolam for fractionated RT.