Introduction: Acute exacerbation of chronic obstructive pulmonary disease (COPD) is a frequent cause of hospitalization and intensive care unit admission. Respiratory failure from airflow obstruction is a direct consequenceof acute airway narrowing.Aim of the study: It was to compare the efficacy of noninvasive mechanical ventilation (NIMV) against conventional mechanical ventilation (CMV) in patients with acute exacerbation of COPD. Patients and methods: Forty patients with acute exacerbation of COPD were recruited in the present study. A comparative, hospital based study design was used. All the cases were examined; clinically and laboratory. The patients were divided into two groups each include 20 patients. Group A received NIMV in the form of continuous positive airway pressure (CPAP) and group B with CMV. Results: There were statistically significant decreases in respiratory rate, heart rate and diastolic blood pressure after 6 hours of CPAP in comparison to baseline parameters in group A. While, there were statistically significant increases in PaO2 and SaO2 after 6 hours of CPAP in comparison to baseline parameters. In group B there were statistically significant decreases in respiratory rate, heart rate, systolic blood pressure and diastolic blood pressure after 6 hours of CMV in comparison to baseline parameters. While, there were statistically significant increases in pH, PaO2, and SaO2 and a statistically significant decrease in PaCO2 after 6 hours of CMV in comparison to baseline parameters. Further, comparison of respiratory rate and hemodynamic parameters in both groups showed statistically significant decreases in respiratory rate, heart rate, systolic blood pressure and diastolic blood pressure in group A in comparison to group B. Finally, failure rate was 35.0% in group A (NIMV) compared to 5.0% in group B (CMV) with statistically significant difference. Conclusions and recommendations: Noninvasive mechanical ventilation is a safe and effective means of improving gas exchange in patients with acute exacerbations of CPPD. If patient not respond to NIMV, CMV should be used. Further studies are needed to evaluate the appropriate selection of patients and to find the best level and schedule of ventilation.