We conducted a retrospective study by reviewing the medical records of 104 patients to assess the usefulness of the objective prognostic score (OPS) in an independent population of Korea. The median survival time (±standard error) of the high OPS group (≥3) was 9.0 ± 1.31 days and that of the low OPS group (<3) was 26.0 ± 3.3 days. The former was significantly shorter than the latter (P < .001). Only delirium (hazard ratio 1.751, P = .032) was related to shorter survival time independent of the OPS. This study demonstrates that the OPS is a valid and useful prognostic tool for predicting survival in terminally ill Korean patients with cancer, and that inclusion of delirium into the OPS may improve its prognostic value.