Aim: In our study, it was aimed to compare the effectiveness of a diffuser mask (OxyMaskTM) and a simple nebulizer set oxygen mask on the blood gas values of patients with the diagnosis of chronic obstructive pulmonary disease (COPD) exacerbation who presented to the emergency department. Materials and Methods: Our research is a prospective, single-blind, randomized controlled study conducted in the Emergency Department of Atatürk University Medical Faculty Hospital. Our study was completed with 213 patients after the exclusion criteria were applied. Of these patients, 93 were administered breathing treatment with a diffuser mask, and 120 were given treatment with a simple nebulizer set oxygen mask. Results: After the treatment with COPD exacerbation, the SO2 and PO2 values of the diffuser mask group were found to be significantly higher than those in the simple oxygen mask group (p<0.05). After the treatment, the PCO2 values of the diffuser mask group were significantly lower than those in the simple oxygen mask group (p<0.05). The diffuser mask also reduced the hospitalization rate of the patients. Conclusion: We suggest that a diffuser mask, which provides better oxygenation in the blood and lowers the carbon dioxide concentration in the blood to a higher extent, can be used in administering breathing treatment to COPD patients with exacerbation who presented to the emergency department with dyspnea.