Spiral (or "helical") computed tomography (CT) was first proposed as a diagnostic tool in suspected pulmonary embolism in the early 1990s'. Because this technique is less invasive than pulmonary angiography and more specific than lung scintigraphy, it has encountered a great success before its real diagnostic value was properly evaluated. On the basis of currently available studies, the following conclusions can be reached: 1. the visualisation of intraluminal filling defect(s) in segmental or more proximal pulmonary arteries is diagnostic of pulmonary embolism; 2. perfusion abnormalities located exclusively in subsegmental or more distal pulmonary arteries are insufficient to confirm the diagnosis of pulmonary embolism; 3. normal spiral CT results are insufficient to rule out the diagnosis of venous thromboembolism and such results can be used only in combination with other tests, such as the assessment of the pretest clinical probability of pulmonary embolism and lower limbs venous ultrasonography, within precise and validated diagnostic algorithms, to make a therapeutic decision. The other main limitations of spiral CT include the injection of iodinate contrast material and a rate of non-diagnostic tests of 4 to 8%.