Introduction and Purpose: Recruitment maneuvers (RMs), which aim to ventilate the collaborated alveolus by temporarily increasing the transpulmonary pressure, have positive effects in relation to respiration, mainly oxygenation. Although many studies have defined the pressure values used during RM and the application period, our knowledge of the effects of different oxygen concentrations is limited. In this study, we aimed to determine the effects of different oxygen concentrations during RM on the arterial oxygenation and respiration mechanics in laparoscopic cases.