The urgency of the resuscitation and the impaired ability of the patient to make a reasonable autonomous decision both conspire against adequate consideration of the principles of medical ethics. Informed consent is usually not possible for these reasons and this leads many to consider that consent is not required for resuscitation, because resuscitation brings benefit and prevents harm and because the patient is not in a position to give or withhold consent. However, consent for resuscitation is required and the common models employed for this purpose are presumed consent or consent from a patient proxy. However, if we are to honour the principles of respect for patient autonomy, as well as beneficence and non-maleficence, when starting and continuing resuscitation we must try and achieve the best balance between benefit and harm from the patient's perspective. The concept of professional substituted judgment involves the resuscitators gathering as much information about the patient as they possibly can, including any previously expressed attitudes towards such a situation, and combining this with their acquired professional knowledge of the likely benefits and harms of the resuscitation endeavour and then exercising their moral imagination, imagining themselves as the patient, and asking "would I want this treatment?" By employing professional substituted judgment resuscitators should recognise when the balance of benefit and harm becomes unfavourable from the patient's perspective and at this point they have a moral obligation to withdraw resuscitation as they can no longer presume the patient's consent. In this way the principles of beneficence, non-maleficence and respect for patient autonomy are more favourably balanced than under other resuscitation decision making processes.