Extracorporeal membrane oxygenation (ECMO) is a procedure that provides extracorporeal mechanical circulatory or respiratory support and is used primarily in patients with life-threatening forms of heart or respiratory failure. There are two basic types of ECMO support: veno-venous (VV) and veno-arterial (VA) ECMO. VV ECMO ensures blood gas exchange and is applied in cases of severe reversible respiratory insufficiency. VA ECMO supports the function of the heart and lungs; other than in reversible forms of damaged heart function, it can also be used in irreversible forms of heart failure as a bridge to heart transplantation or to the implantation of mechanical circulatory support device. ECMO is an invasive and technically complex procedure that is performed in critically ill patients and thus has a high risk of complications. Results of ECMO treatment vary depending on the indications for the procedure itself. Patients in whom ECMO was applied for respiratory support show better outcomes compared with those with cardiogenic shock or cardiac arrest. Despite a lack of evidence based on large randomized studies to support its application, in clinical practice ECMO represents a life-saving method of treatment in well-selected critical patients.