Background: CRD is extremely distressing but treatable symptom to the advanced cancer patients (ACP). There are limited studies to evaluate the frequency and characteristics of CRD. The aim of this study was to identify the frequency, and factors associated with severity of CRD. Secondary aim was to determine the screening performance Edmonton Symptom Assessment Scale (ESAS)-drowsiness item against the Epworth Sleepiness Scale (ESS). Methods: We prospectively assessed 180 consecutive ACP at a tertiary cancer hospital. After obtaining signed consent, the patients completed ESAS, Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI); ESS (≥10 diagnostic of CRD), Hospital Anxiety Depression Scale (HADS), STOP-Bang Screening Scale (SBS), and Screening tool for RLS. We determined epidemiological performance, spearman correlations, regression analysis, receiver operated characteristics of CRD. Results: Of the180 patients assessed, 51% were female, CRD was found in 50% ACP, median scores(IQR) ESS: 11(7-14); ESAS- drowsiness item was 5 (2-6); PSQI was 8(5-11); ISI (13 (5-19); SBS 3(2-4); HADS-D 6(3-10). Sleep apnea was found in 61%; and RLS in 38%. ESAS-D was associated with other ESAS items[r, p-value] Sleep (0.38, < 0.0001); pain (0.3, < 0.0001); fatigue(0.51, < 0.0001); depression(0.39, < 0.0001); anxiety(0.44, < 0.0001); shortness of breath(0.32, < 0.0001); anorexia(0.36, < 0.0001), FWB(0.41, < 0.0001), and ESS (0.24, 0.001), Opioid dose [MEDD] (0.19, 0.01). Multivariate analysis found no independent predictors except ISI (OR 2.35; 0.036), ESAS Fatigue (OR 9.08, <0.0001), ESAS Anxiety (3.0, 0.009); feeling of well-being (OR 2.27, p=0.04). An ESAS- drowsiness cut-off score of ≥ 3(of 10) resulted in a sensitivity and specificity of 81% and 32% and of 70% and 44% in the training and validation samples, respectively. Conclusions: Clinically significant CRD was associated with increased fatigue, anxiety, sleep disturbance and worse feeling of well-being. These symptoms should be routinely assessed and treated in ACP with CRD. ESAS-drowsiness score of ≥3 of 10 is most useful for screening CRD.