Tracheo-innominate artery fistula (TIF) is one of the most important complications of tracheostomy in that it is often life threatening. We experienced two cases with TIF and tracheo-innominate artery allovascularity, in which three-dimensional helical CT (3DCT) was useful in making the diagnosis of TIF and tracheo-innominate artery allovascularity. In one case, acute hemorrhage occurred during the procedure of routine tube exchange, and hemostasis was achieved by inflating the cuff of the tracheostomy tube. After TIF was confirmed by 3DCT, surgical ligation of the innominate artery was performed. In the other case, the recognition of a pulsating movement of the tracheostomy tube prompted us to perform 3DCT, which demonstrated a collateral branch from the innominate artery to the trachea. Laryngotracheal separation was performed to prevent hemorrhagic events in the future. For patients with severe neurological disorders, 3DCT has the advantage that only a short time is required to produce a digital image demonstrating the structure surrounding the trachea, which is necessary for the management of the patients' airway.