Although palliative sedation therapy (PST) is considered to alleviate intolerable and refractory symptoms in dying patients with advanced cancer, there have been few studies regarding the situation of tertiary cancer center. We conducted a retrospective survey of the medical records of the patients who died between April 2015 and March 2016 at the National Cancer Center Hospital in Japan. PST was conducted in 75 out of 431 patients (17.4%). The patient demographics were as follows: sex (male/female), 48/27; median age, 61 years (range 5-83; 11 patients (14.7%) were aged under 39 years); and primary sites were lung, 18 (24.7%)/ pancreas, 11 (14.7%)/ hematopoietic organs, 11 (14.7%)/ bones and soft tissues, 8 (10.7%)/ and the others, 27 (36.0%). The main target symptoms for PST were dyspnea (38, 50.7%) and delirium (30, 40.0%). The most commonly used sedative agent was midazolam (72, 96.0%). Continuous deep sedation was intended in 61 patients (81.3%) at the death. Median survival from the start of PST were 2 days (range 0-54). The differences between palliative care team (PCT) intervention group and control group were lower age (58 vs. 62.5, P=0.048) and uniformity of initial midazolam dose (5-12 vs. 9.6-25.2 mg/day). Distinctive feature in this study was large proportion of adolescent and young adult patients with rare cancers. PCT might have different approaches to sedation in comparison to non-PCT medical staffs.