Purpose of Review: To describe the impact of oxygen and carbon dioxide management on patient outcomes following cardiac arrest. Recent Findings: Although there are no data that suggest that supplemental oxygen administration during cardiopulmonary resuscitation is harmful, there is concern that 100 oxygen during the postresuscitation phase may be undesirable. The evidence to avoid hyperoxia is limited to animal studies and retrospective clinical studies that examine the association between exposure and outcome. There is a correlation between end-tidal carbon dioxide values during cardiopulmonary resuscitation and resuscitation outcome, yet this correlation is likely to reflect low or absent cardiac output and be a biomarker of illness severity rather than a mediator of injury. Additionally, very limited high-level human data exist on the relationship between arterial carbon dioxide tension and outcome following cardiac arrest. Retrospective studies have identified hypocapnia in the intensive care unit as being independently associated with worse neurological and mortality outcomes in cardiac arrest patients. Although there appears to be sufficient evidence to recommend avoiding hypocapnia after resuscitation, observational data suggest that hypercapnia may be independently associated with a greater likelihood of discharge home amongst cardiac arrest survivors. Summary: Current data for oxygen and carbon dioxide management following resuscitation suggest that hyperoxia and hypocapnia may be injurious and should be avoided, and that mild hypercapnia may increase the likelihood of discharge home amongst survivors. Such data should be viewed as hypothesis generating. Randomized controlled trials have commenced to clarify the safety, feasibility and efficacy of targeting different oxygen and carbon dioxide tensions following cardiac arrest.