Introduction: In recent years there has been increase in the number of patients who need thoracic surgery – first of all different types of pulmonary resection because of primary bronchial cancer, and very often among patients whose lung function is impaired due to different degree of bronchial obstruction so it is necessary to assess functional status before and after lung surgery to avoid the development of respiratory insufficiency. Objective: To show the changes in the level of arterial blood gases after various ranges of lung resection. Material and methods: The study was done on 71 patients surgically treated at the Clinic for Thoracic Surgery KCU Sarajevo, who were previously treated at the Clinic for Pulmonary Diseases “Podhrastovi” in the period from 01. 06. 2009. to 01. 09. 2011. Different types of lung resection were made. Patients whose percentage of ppoFEV1 was (prognosed postoperative FEV1) was less than 30% of normal values of FEV1 for that patients were not given a permission for lung resection. We monitored the changes in levels-partial pressures of blood gases (PaO2, PaCO2 and SaO2) one and two months after resection and compared them to preoperative values. As there were no significant differences between the values obtained one and two months after surgery, in the results we showed arterial blood gas analysis obtained two months after surgical resection. Results were statistically analyzed by SPSS and Microsoft Office Excel. Statistical significance was determined at an interval of 95%. Results: In 59 patients (83%) there was an increase, and in 12 patients (17%) there was a decrease of PaO2, compared to preoperative values. In 58 patients (82%) there was a decrease, and in 13 patients (18%) there was an increase in PaCO2, compared to preoperative values. For all subjects (group as whole): The value of the PaO2 was significantly increased after lung surgery compared to preoperative values (p <0.05) so is the value of the SaO2%. The value of the PaCO2 was significantly decreased after lung surgery compared to preoperative values (p <0.05). Respiratory insufficiency was developed in none of patients. Conclusion: If the % ppoFEV1 (% prognosed postoperative FEV1) is bigger than 30% of normal values of FEV1 (according to sex, weight, height, age) in patient planned for lung resection surgery there is no development of respiratory insufficiency after resection.