Univent tube (UT) and EZ-blocker were used for one-lung ventilation (OLV). UT is a single lumen tube with a small separate lumen containing a bronchial blocker. EZ-blocker differs with its unique y-shaped double-cuffed distal end. We aimed to compare these two airway devices effects on airway pressures, oxygenation, ventilation and haemodynamics during OLV. Patients undergoing elective thoracotomy for the first time were included in this prospective randomized study. Patients were divided into two groups as UT and EZ. Bronchial blockers (BB) placement time was recorded. In lateral decubitus position, airway pressures, static compliance, tidal volume (TV), respiratory rate (RR) and haemodynamic findings were recorded before inflating the BB cuff (Pre-OLV) and during OLV every 15 min. Arterial blood gas (ABG) samples were obtained before and during OLV. 70 patients were enrolled in the study. The demographic characteristics and data related to anesthesia and surgery were similar in both groups. It took longer to place EZ than UT (p = 0.02). P-peak values were similar in both groups. P-plateau was significantly lower at the beginning of OLV (OLV15th min) and higher at the end of OLV (pre-DLV) in EZ group compared to UT (p = 0.01, p = 0.03). C-static were significantly higher at the beginning of OLV (OLV15th min) in EZ group compared to UT (p = 0.01). During the following measurements, C-static values were similar for both groups. Ventilation were achieved with similar TV and RR. ABG findings and haemodynamic variables were similar. EZ and Univent tube affected the airway pressures, oxygenation, ventilation and haemodynamic variables similarly during OLV in patients with normal respiratory function. These devices can be alternatives to each other based on clinical conditions.