Pulmonary embolism is a common clinical problem that is associated with considerable morbidity and mortality. Although early diagnosis of pulmonary embolism is one of the critical factors affecting outcomes, clinical presentation is often nonspecific and can mimic that of several other conditions. Therefore, clinicians often have to rely on a combination of physical examination and laboratory resultsd and imaging tests to determine the correct diagnosis. Currently, imaging offers a variety of fast and accurate tests that can provide anatomic and functional information, thus allowing early diagnosis. Nowadays, CT angiography represents the cornerstone of diagnostic evaluation of pulmonary embolism and new technological improvements, such as Dual Source CT, have increased the accuracy of CT in this clinical setting. Nevertheless, concerns about radiation exposure and side effects of contrast medium administration with CT angiography indicate that a role for ventilation/perfusion scintigraphy in the evaluation of patients with suspected pulmonary embolism is still to consider. In this chapter we will review the CT pulmonary angiography protocols, the CT findings of acute pulmonary embolism, we will describe some pitfalls that can led to pulmonary embolism misdiagnosis. Furthermore, we will compare the diagnostic performance of ventilation-perfusion scintigraphy vs CT angiography and present some cases of non-thrombotic causes of pulmonary embolism.