Objective To explore the effects of lateral position ventilation on lung volume and oxygenation in patients with acute respiratory distress syndrome ( ARDS) . Methods Fourteen patients with ARDS were enrolled. Supine position, lateral position and supine position were successively adopted and continued for one hour respectively. End-expiratory lung volume ( EELV) was measured at the end of each epoch. Effects of different position on gas exchange, lung mechanics and hemodynamics were monitored.Results EELV was increased from ( 1109 ±321) mL to ( 1376 ±381) mL after lateral ventilation ( P lt;0. 05) , and decreased to ( 1143 ±376) mL after the second supine ventilation ( P lt;0. 05) . Compared with initial supine ventilation, there was no significant difference in EELV after the second supine ventilation( P gt;0. 05) . PaO2 /FiO2 was increased from ( 154. 3 ±35. 0) mm Hg to ( 189. 9 ±60. 1) mm Hg after lateral ventilation ( P lt;0. 05) , and increased to ( 209. 2 ±75. 4) mm Hg after the second supine ventilation ( P lt; 0. 05) . Compared with initial supine ventilation, PaO2 /FiO2 was increased greatly after the secondsupine ventilation ( P lt; 0. 01) . There was no significant difference in PaCO2 , lung mechanics and hemodynamics after changing different position. Conclusion Lateral position ventilation can increase EELV and improve oxygenation in patients with ARDS.