STUDY OBJECTIVE: Comparison of flow-controlled ventilation (FCV) to standard of pressure-controlled ventilation (PCV) in thoracic surgery procedures requiring one-lung ventilation. DESIGN: Prospective, non-blinded, randomized, controlled trial. SETTING: Operating theater at a university hospital, Austria. PATIENTS: Patients scheduled for elective, thoracic surgery. INTERVENTIONS: Participants received ventilation randomly either with FCV or PCV per-protocol for the duration of anesthesia. MEASUREMENTS: The primary endpoint was oxygenation assessed by paO MAIN RESULTS: A total of 46 patients were enrolled and 43 included in the primary analysis. The primary endpoint paO CONCLUSIONS: In this single-center randomized controlled trial, flow-controlled ventilation improved gas exchange parameters in terms of oxygenation and carbon dioxide removal during one-lung ventilation in patients undergoing thoracic surgery and reduced the mechanical impact of artificial ventilation.