As emphasized in Part 1 of these guidelines, the diagnosis of pulmonary embolism (PE) is confirmed or refuted using ventilation/perfusion scintigraphy (V/P(SCAN)) or multidetector computed tomography of the pulmonary arteries (MDCT). To reduce the costs, the risks associated with false-negative and false-positive diagnoses, and unnecessary radiation exposure, preimaging assessment of clinical probability is recommended. Diagnostic accuracy is approximately equal for MDCT and planar V/P(SCAN) and better for tomography (V/P(SPECT)). V/P(SPECT) is feasible in about 99% of patients, while MDCT is often contraindicated. As MDCT is more readily available, access to both techniques is vital for the diagnosis of PE. V/P(SPECT) gives an effective radiation dose of 1.2-2 mSv. For V/P(SPECT), the effective dose is about 35-40% and the absorbed dose to the female breast 4% of the dose from MDCT performed with a dose-saving protocol. V/P(SPECT) is recommended as a first-line procedure in patients with suspected PE. It is particularly favoured in young patients, especially females, during pregnancy, and for follow-up and research.