Acute pulmonary embolism (PE) diagnosis is a challenging task, despite the advanced diagnostic methods for both clinicians and radiologists. Awareness of the "hyperdense lumen sign" in patients obtained un-enhanced computarized tomography (CT) of chest mayhelp to establish an acute PE diagnosis, especially in clinically non suspected PE patients. A 78-year-old woman was brought to our emergency department (ED) with an aphasia complaint. The patient's dizziness improved in ED. Neurological examination returned to base line status but sinus tachycardia and low saturation value on room air were continuing. Un-enhanced CT of the chest demonstrates hyperdense material within the right main pulmonary artery. Contrast-enhanced CTPA demonstrated hypodense filling defect within the rigth main pulmonary artery consistent with PE. Independent of the patient's complaint, the measurement of all vital signs is important especially in elderly patients. Emergency physicians have to be aware of that the "hyperdense lumen sign" may point out PE and should be prevented from delayed recognition.