Background: Radiation therapy is a cornerstone in the treatment of cancer in children. Although painless, there is a requirement for the child to lie still by themselves in the radiation treatment room. Most RT services use intravenous sedation or anesthesia. The aim of the study was to describe the technique of inhalational anesthesia with sevoflurane without venoclysis for general anesthesia during RT from January to December 2022, as a pilot project in 25 children. Methods:It is an observational, descriptive, and prospective study of a series of cases. Pediatric patients aged 2 to 13 years diagnosed with cancer, underwent RT under sevoflurane anesthesia without venous access. RT is performed five days a week, with only Tuesdays selected, with the same anesthesiologist and anesthesia resident. patients were monitored with a cardioscope, pulse oximetry, capnography, and gas analyzer. During the procedure, the following were evaluated: the expired fraction of sevoflurane and the corresponding Minimum Alveolar Concentration (MAC) for induction and maintenance, anesthesia and awakening time, place and time of irradiation, and immediate and late adverse effects (after awakening until discharge hospital). Finally, the time of hospital discharge and complications were evaluated after completion. Results: A total of 25 patients diagnosed with cancer and receiving radiotherapy were studied. No difference was observed between genders, with 96% of children between 2 and 8 years old, and 60% being 4 and 5-yearold children. Sevoflurane was administered to 100.0% of patients in all treatment sessions. Mean anesthesia time was 22.96 minutes, mean irradiation time was 10.84 minutes, and mean awakening time was 6.12