We studied a regionally based cohort of 483 consecutive patients with colorectal cancer referred for chemotherapy and/or radiotherapy. These patients were assessed and managed according to consistent policies. We investigated the effects of socio-economic deprivation and comorbidity upon survival. Significant comorbidity was present in 48% of the patients. Overall survival and cause-specific survival were summarized using Kaplan-Meier curves. Equality of survivor functions was assessed using the logrank procedure and Cox's proportional hazards analysis. In univariate analysis, the following variables significantly affected survival: comorbidity, performance status, age and clinical stage. We could find no correlation between deprivation and comorbidity. The presence of comorbidity significantly affected cause-specific survival (3-year cause-specific survival without comorbidity 54.2%; with comorbidity 44.6%). In adjusted analysis, deprivation had an independently adverse effect on overall survival, hazard ratio 1.04 (95% confidence interval 1.00–1.08), but this was only of borderline statistical significance, P = 0.049. This study demonstrates that the interrelationships between comorbidity, deprivation and outcome in this group of patients are complex: even when care is readily available, patient assessments are uniform, and clinical decision making is consistent.