Abstract： Objective To evaluate the effect of end-tidal carbon dioxide (EtCO2) detection for location of the leading bronchus in patients with pneumothorax.Methods Transbronchoscopic EtCO2 detection was performed in 4 patients with intractable pneumothorax in whom transbronchoscopic balloon detection failed to localize the leading bronchus.A specific bronchus was suspected to be the leading bronchus when its EtCO2 value was significantly lower than that of the main bronchus of the affected lung.After the pleural air leakage was successfully sealed by bronchial occlusion of the suspected bronchus,the EtCO2 was confirmed to indicate the leading bronchus.Results Transbronchoscopic EtCO2 detection successfully located the leading bronchus in all 4 patients.Conclusion Transbronchoscopic EtCO2 detection is a new method of locating the leading bronchus in patients with intractable pneumothorax.