Purpose: Although, for patients with cancer, comorbidity can affect the timing of cancer detection, treatment, and prognosis, there is little information relating to the question of whether the choice of comorbidity index affects the results of studies. Therefore, to compare the association of comorbidity with mortality after surgery for colon cancer, this study evaluated the Adult Comorbidity Evaluation-27 (ACE-27), the National Institute on Aging (NIA) and National Cancer Institute (NCI) Comorbidity Index, and the Charlson Comorbidity Index (CCI). Patients and Methods: The study population consisted of colon cancer patients (N = 496) who underwent surgery at the University of Alabama at Birmingham Hospital from 1981 to 2002. Hazard ratios (HRs) with 95% CIs were obtained using the method of Cox proportional hazards for the three comorbidity indices in predicting overall and colon cancer-specific mortality. The point estimates obtained for comorbidity and other risk factors across the three models were compared. Results: For each index, the highest comorbidity burden was significantly associated with poorer overall survival (ACE-27: HR = 1.63; 95% CI, 1.24 to 2.15; NIA/NCI: HR = 1.83; 95% CI, 1.29 to 2.61; CCI: HR = 1.46; 95% CI, 1.14 to 1.88) as well as colon cancer-specific survival. For the other risk factors, there was little variation in the point estimates across the three models. Conclusion: The results obtained from these three indices were strikingly similar. For patients with severe comorbidity, all three indices were statistically significant in predicting shorter survival after surgery for colon cancer. © 2009 by American Society of Clinical Oncology.