The aim of this study was to assess the prevalence of delirium in advanced cancer patients admitted to different palliative care services in Italy and possible related factors. The secondary outcome was to assess the changes of delirium after 1week of palliative care. A consecutive sample of patients was screened for delirium in period of 1year in seven palliative care services. General data, including primary tumor, age, gender, concomitant disease, palliative prognostic score (PaP), and Karnofsky status, were collected. Possible causes or factors associated with delirium were looked for. The Edmonton Symptom Assessment Scale was used to assess physical and psychological symptoms and the Memorial Delirium Assessment Scale (MDAS) to assess the cognitive status of patients, at admission (T0) and 1week after palliative care (T7). Of 848 patients screened, 263 patients were evaluated. Sixty-six patients had only the initial evaluation. The mean Karnofsky status was 34.1 (SD=6.69); the mean PaP score at admission was 6.9 (SD=3.97). The mean duration of palliative care assistance, equivalent to survival, was 38.4days (SD=48, range 2-220). The mean MDAS values at admission and after 1week of palliative care were 6.9 (SD=6.71) and 8.8 (SD=8.26), respectively. One hundred ten patients (41.8%) and 167 patients (67.3%) had MDAS values ≥7 at admission and after 1week of palliative care, respectively. Age, dehydration, cachexia, chemotherapy in the last three months, and intensity of drowsiness and dyspnea were independently associated with a MDAS>7. A worsening of drowsiness, the use of opioids, and the use of corticosteroids were independently associated with changes of MDAS from T0 to T7. Although the prevalence of delirium seems to be similar to that reported in other acute settings, delirium tended to worsen or poorly responded to a palliative care treatment. Some clinical factors were independently associated with delirium. This information is relevant for decision-making when delirium does not change despite a traditional intervention. Continuous assessment of delirium should be performed in these settings to detect deterioration of cognitive function. Further studies should elucidate whether an earlier approach to palliative care would decrease the prevalence of delirium at a late stage of disease.