The fundamental role of the cardio-respiratory system is to supply the tissues with adequate amount of oxygen to cover their metabolic need. Acute lung injury and acute respiratory distress syndrome are characterized by atelectasis of the alveoli, causing inadequate gas exchange in the lung and lack of oxygen supply to the body. Under these circumstances by increasing the FiO2 only may not be enough to improve oxygenation. One of the possible alternatives is the lung recruitment manoeuvre, during which the alveoli are opened up with high inflation pressure and to keep them open by maintaining appropriate positive end expiratory pressure. However, high intrathoracic pressures may cause haemodynamic instability by affecting the work of the heart and compressing the mediastinal veins. It is uncertain, how haemodynamics are best monitored during lung recruitment. Is continuous monitoring of the mean arterial pressure and the central venous pressure enough, or do we need to measure invasive haemodynamic parameters such as cardiac output and intrathoracic blood volume during such an aggressive intervention?. The aim of this article is to give a review of the possible answers for these questions based on the results of physiological and recently published clinical and experimental research. Key words: lung recruitment, acute respiratory distress syndrome, positive end expiratory pressure, extravascular lung water, oxygenation, hemodynamic monitoring.