Background: Research has shown that informal caregivers provide substantial psychosocial and material support to advanced cancer patients. Few studies have examined how family caregivers influence patients’ advance care planning. Here we test whether patients’ perceptions of their caregivers’ preference for comfort (vs. life-extending) end-of-life (EOL) care is associated with DNR order completion. We also evaluated whether caregivers’ actual agreement with patients on preference for comfort EOL care was associated with their rates of DNR order completion. Methods: Coping with Cancer II is an NCI –funded, multi-site, prospective cohort study of patients with advanced cancer and their informal family caregivers. Patients are interviewed after receiving restaging scan results and asked if they would prefer a plan of EOL care focused on life-extension or one focused on relieving pain. Patients are also asked what type of EOL care they think their family caregivers would prefer for them and whether or not a DNR order has been completed for them. Caregivers are interviewed separately after patients receive restaging scan results and asked what type of EOL care they would want for the patient. Results: Based on patient data alone (N=72), patients who preferred comfort care at the EOL and who believe that their family caregiver agrees with them on this were significantly more likely than others to report DNR order completion (OR=3.67, p=0.013). Based on data from both patients and caregivers, patients’ perception of agreement with their caregivers on desire for comfort EOL care was more strongly associated with patients’ reports of DNR completion (r_s=0.51, p=0.004) than was actual agreement with their caregivers on desire for comfort EOL care (r_s=0.36, p=0.045). Conclusions: Patients who prefer comfort care to life-extending care at the EOL, and who think that their caregivers also want them to pursue comfort care, are more likely to have a DNR order completed. Interestingly, patients’ perception of this agreement had a stronger influence on DNR completion than the caregivers’ actual agreement with patients’ preference for comfort EOL care. DNR completion is influenced by patients’ perceptions of family support.