Pulmonary artery sarcomas are commonly misdiagnosed as pulmonary emboli, and differentiation on initial imaging can often be difficult. However, several features, if identified correctly, should raise pulmonary artery sarcoma among diagnostic possibilities. First, a low attenuation filling defect occupying the entire luminal diameter of the main or proximal pulmonary artery branches with expansion of these vessels should raise the possibility of a pulmonary artery sarcoma. These findings are uncommon in pulmonary emboli. Second, extraluminal extension into the lung parenchyma is a common finding in pulmonary artery sarcomas, but should not be seen in pulmonary emboli. Third, although rarely performed, a noncontrast chest CT scan will generally demonstrate hyperattenuation in the setting of larger pulmonary emboli, whereas pulmonary artery sarcomas will display relatively low attenuation prior to contrast administration. Fourth, patients with pulmonary artery sarcomas tend to have more indolent symptoms and a relative paucity of symptoms, with clinical presentations disproportionately mild in comparison with the degree and size of filling defects within the pulmonary arteries. Finally, pulmonary emboli respond to anticoagulation therapy, thrombolytic therapy, or both, whereas pulmonary artery sarcomas do not.