Background and Purpose:Trauma is considered to be one of the main causes of death in the world and the number of deaths caused by traumatic incidents has experienced an annual increase of 15%. Despite this fact that comprehensive information on the incidence of pulmonary complications in traumatic patients, the patients' fate in the country and factors affecting it is not available, the present study was conducted to determine the incidence of these complications and the main factors causing them in patients with traumatic injuries visiting the emergency room of the largest medical, educational, and research center in the province, which is considered to be the most important transfer center for traumatic patients from other medical centers in the region. Methods: This is a cross-sectional prospective study conducted on the injured people who visited the emergency room of Imam Reza Hospital in Tabriz in 2015. The incidence of pulmonary complications and factors affecting them were recorded in a valid and reliable researcher-developed checklist that included demographic information and information related to the incident. The significance level was set at p < 0.05. Results: Of all the 482 traumatic patients, 63.5% were men with a mean age of 41.6±15.4, with pulmonary complications reported in 48.1% of them. Pneumonia was the most common complication among these patients which was reported in 161 (33.4%) patients, and pneumothorax and ARDS were the second and third most common complications with the frequencies 41 (8.5%) and 39 (8.1%), respectively. The main causes of the incidence of pulmonary complications were reported to be an age of above 45 (p < 0.001), reduced consciousness level based on GCS criterion (p = 0.01), single trauma to the chest (p < 0.001), synchronous trauma to the chest and other organs (p < 0.001), hospitalizations of longer than one week (p < 0.001), intubation (p < 0.001) and finally transfer of the patient to the operation room (p < 0.001). It should be noted that a pulse rate of more than 100 beats in a minute was accompanied by a decrease in the incidence of pulmonary complications (p = 0.01). In the evaluation of the patients' fate, it was found out that only 15 (3.1%) patients were discharged from the emergency room. Finally, 34 patients (7.05%) died during the study, with the age group 15-29 years accounting for one third of the patients investigated. Pneumonia (33.4%) was the most common pulmonary complication. For 152 patients (34.8%) the duration of hospitalization was longer than seven days. Conclusion: The fact that the incidence of pulmonary complications in traumatic patients visiting the Location of research was 48.1% highlights the need for further attention to and proper management of complications in these patients. Delayed pulmonary complications are more common among traumatic patients, since the most common complication in this study was reported to be delayed pneumonia. Therefore, given the significance of such a high incidence, further studies and taking effective prev...