Chest tube insertion is one of the common and critical procedures in emergency room. The most common tool for chest tube position confirmation is chest x-ray. The aim of this case report is to explain one of pitfalls of this tool in confirmation of chest tube position. The patient was a 36-year-old man who had been transferred to ED by EMS due to blunt chest trauma in a motor vehicle collision. After detecting pneumothorax in chest CT scan, chest tube has been inserted and chest x ray has been done for chest tube`s place confirmation. X-ray ascertains that the tube is in the right place but lung does not expand and dyspnea does not improve completely. In chest CT scan which will be done after 2 days, it reveals that chest tube was in subcutaneous tissue. Although chest x-ray is a useful modality to confirm chest tube placement, chest tube function can define important information and imaging should be interpreted beside clinical coarse. It should be noted that in the case of current report, the physical examination is used.