Pulmonary embolism is one of the most frequent causes of acute and chronic respiratory failure in patients with COPD exacerbations. In hospital admissions secondary to COPD exacerbations, pulmonary embolism must be kept in mind if there is no cause of exacerbation. The similar symptoms of COPD exacerbations and pulmonary embolism cause difficulties in making the diagnosis of PE in such COPD patients. CT angiography must be the first line diagnostic tool in order to its advantages in differential diagnosis and not having the false of scintigraphy in COPD patients. All hospitalized COPD patients must be considered for thromboembolic prophylaxis.