objective To compare three risk prediction system,the physiological and operative severity score for the enumeration of mortality and morbidity(POSSUM),the Portsmouth POSSUM (P-POSSUM)and the colorectal POSSUM(Cr-POSSUM)for the accuracy in predicting operative mortality of patients of colorectal cancer in a single Chinese referral hospital setting. Methods Data of 903 patients,who undergone surgery for colon and rectal cancers from 1992 to 2005 at Peking University Third Hospital,were enrolled in the study.POSSUM,P-POSSUM and Cr-POSSUM was used respectively to predict the mortality rate.ROC curve was applied to judge the differentiation ability of each score.Model goodness-or-fit was tested by the Hosmer-Lemeshow statistic and subgroup analysis was performed by the ratio of observed to expected deaths(O∶E ratio). Results The actual inhospital mortality in our series was 1.0%(9/903).The oredicted mortality rate by POSSUM,P-POSSUM and Cr-POSSUM were 5.6%,2.8% and 4.8%respectively.These predicted mortality rate were significantly higher than actual mortality of our patients.The O∶E ratio was 0.18,0.35 and 0.2 respectively. Conclusion The predicted mortality rate of POSSUM,P-POSSUM and Cr-POSSUM were significantly higher than actual observed mortality rate in a single Chinese referral hospital for patients of colorectal cancer.