The complications of a tracheotomy are caused by inappropriate surgical techniques, unsuitable cannula selections, and improper wound care. Among these, the solutions to problems of surgical technique and wound care have been reported in many articles. Detailed methods for preventing complications by the cannula are rare. The authors tried to find a way of preventing complications by the cannula Materials and Methods : The authors analized complications in 70 patients who had a temporary tracheotomy and were wearing a cannula. And the complications were compared between 4 commercial cannulas used in our institute. The examination methods used were a simple neck lateral radiogram and flexible endoscopy. Results： The order of most commonly found complications were as followed; at the suprastoma, end of cannula, level of tracheotomy, and infrastoma. Among 4 cannulas, a particular product had so many complications compared to the other 3 cannulas. The most common cause of complications was unsuitable cannula. All complications were cured with no sequelae. Flexible endoscopy is far superior to radiologic exam for detecting tracheal complications. Conclusion： Flexible endoscopy through the tracheostoma is very helpful for detecting complications early and determining if a proper cannula is used, which can prevent further complications such as stenosis or innominate artery rupture. The authors, therfore, recommend using the flexible endoscopy to all patients wearing tracheotomy tubes. Some complications can simply be prevented by replacing the one to another cannula properly fit for the individual patients. Various cannulas should be prepared at the hospital because the tracheal curvature and distance of skin to trachea are individualized.