The aim of this work was to determine the effect of lung recruitment on oxygenation, respiratory mechanics and ventilation and adjustment of PEEP. This study included twenty patients who were mechanically ventilated due to respiratory failure for different causes. All patients had refractory hypoxaemia. Two recruitment maneuvers (RMs) were applied (for all patients), with 20 minutes interval. Oxygenation parameters, respiratory mechanics and ventilation were recorded before RMs (at baseline or RM0), after the first RM (RM1) and after the second RM (RM2). Hemodynamic monitoring was done all through the study. Also any complications as barotrauma were observed. It was found that RMs resulted in statistically significant improvement in oxygenation parameters (including PaO2, P(A-a) O2 , shunt fraction, PaO2/ FIO2 and PaO2 / PAO2). Respiratory mechanics showed no significant change except for dynamic compliance, which showed statistically significant increase after the second RM. But both static compliance and airway resistance did not have significant change. Ventilation, represented by PaCO2, showed a statistically significant improvement after RMs. No hemodynamic compromise or barotrauma were observed.