Tracheal bronchus (TB) is an aberrant, accessary or ectopic bronchus arising almost exclusively from the right side of the tracheal wall above the carina. In our center, 673 bronchoscopic examinations were performed from 2009 to 2011 in patients undergoing one lung ventilation (OLV) and 3 TB were found. The incidence of a TB at bronchoscopy was 0.45% in our research, which is consistent with the reported incidence range from 0.1-5%. The clinician should consider the possibility of anomalous right upper lobe bronchus and perform bronchoscopy prior to the right bronchial blocker insertion, when left-sided OLV using bronchial blocker is planned. Also, for the patient with TB, a double lumen tube insertion is recommended than a blocker insertion to achieve OLV completely.