BACKGROUND Seriously or terminally ill patients are frequently incapacitated and unable to express their preferences regarding cardiopulmonary resuscitation (CPR). In this situation, family members or other surrogate decision makers are often asked whether they believe the patient would want to be resuscitated. We evaluated the concordance of patient CPR preferences and surrogate perceptions of the patient preferences in the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT), a large, multicenter study of seriously ill hospitalized patients. METHODS We compared patient preferences and surrogate perceptions in 1226 pairings in which both patient and surrogate responded to CPR decision questions. We also examined factors that might influence patient-surrogate concordance. RESULTS Twenty-nine percent of patients with paired data did not want to be resuscitated; 26% of surrogates did not believe the patient they represented would want to be resuscitated. Within pairs, the overall exact agreement with respect to CPR decisions was 74%. For patients favoring CPR, only 16% of the surrogates misconstrued the patient's wishes. For patients who did not want to be resuscitated, however, 50% of the surrogates did not reflect the patient's wishes. If patients reported telling surrogates their CPR preference, concordance was significantly improved if the surrogate believed the patient did not want to be resuscitated and was significantly worsened if the surrogate believed the patient wanted CPR. This finding is likely an artifact of patients being more likely to report their preference to surrogates if that preference was not to be resuscitated. CONCLUSIONS Surrogates' perceptions of patient CPR preferences are often inaccurate, particularly for those patients who do not want to be resuscitated. Methods to improve communication between patients and surrogates on CPR preferences should be developed and evaluated.