Historically ARDS was associated with case fatality rate greater than 50%. Breakthroughs in medicine, especially in intensive care, gradually increased survival rate of ARDS patients. CESAR and ANZ ECMO studies published in 2009. brought new evidence about successful use of ECMO support in treatment of severe ARDS in adults, increasing the survival rate to about 70%. ECMO support can be divided into venoarterial, which provides oxygenation and hemodynamic support, and venovenous, which serves as an artificial lung. Due to the complexity and increased risk of complications ECMO support is being held at specialised centers with highly trained personnel. Legionnaires' disease which clinically manifests as atypical pneumonia is caused by L.pneumophila. Fresh water systems are natural habitat of legionella, most frequently people become infected through inhalation of contaminated water droplets. It is estimated that it causes up to 9% of community aquired pneumonias, and has case fatality rate around 10%. Diagnosis is most commonly established through urinary antigen testing. Rapid and correct diagnosis is of great significance, as early start of the correct treatment is related to better patient outcome. The case report shows a 33 year old former intravenous drug user male patient, who presents with acute liver injury, jaundice, and severe pneumonia. The patient is hospitalised, and initial antibiotic therapy consisted of meropenem, vancomycin, metronidazole is started. Diagnosis of legionnaires' disease is established late, 13 days after the first symptoms. During hospitalisation, patient's condition progressively deteriorated. As the ARDS developed, patient was put on mechanical ventilation, and shortly after transferred by air medical services to the ECMO center. For 27 days patient was dependant on VV ECMO support, and thereafter for 9 days on mechanical ventilation. The treatment was complicated with ventilator associated pneumonia, which was treated successfully. On one year follow-up patient was without functional deficits. This thesis gives a short review of facts about ARDS, VV ECMO, legionnaires' disease, and presents a case of severe ARDS caused by legionnaires' disease successfully treated with VV ECMO support. It contributes, in small amount, to constantly growing body of evidence in use of ECMO for ARDS.