The aims of this study were to investigate the impact of medical and non-medical factors on the cardiopulmonary resuscitation (CPR) preferences of patients, to determine which of them are the most important to patients when considering CPR, and to compare the views of older (> or = 70 years) and younger (< 70 years) patients. We interviewed 180 patients, 86 of whom were aged 70 years or older. 'I do not want to be a burden on my family' was the most important factor for older patients, and they were more ready to leave the decision to the doctor than were the younger patients. 'I want to retain my capacity to think clearly' was most important to younger patients. In general, younger patients gave higher ratings in favour of CPR than older patients. Increased age, drug abuse, dementia, pain, poor functional status and a low likelihood of success were associated with a lower preference rating for CPR in both age groups.