BACKGROUND: Pulmonary thromboembolism(PTE) is a life threatening disease that needs early diagnosis. Spiral CT angiography depict thromboemboli in the central pulmonary vessels with greater than 90% sensitivity and specificity, which approaches the results of pulmonary angiography in the Prospective Investigation of Pulmonary value(clinical utility) of the spiral CT angiography with 2D image (multiplanar reformation) and 3D images(Shaded surface display, Minimal intensity projection) in the pulmonary thromboembolism. METHODS: We retrospectively analysed spiral CT angiography and prlmonary angiography, lung scan and clinical recordings of 20 patients who had PTE diagnosed by spiral CT angiography(n=19 cases) or pulmonary angiography(n=1 case) from September 1997 to August 1998. Among 20 patients who had underwent spiral CT angiography, 14 patients could be performed lung perfusion scan at the same time. We analyzed the vascular and parenchymal change in spiral CT angiogram. RESULTS: Anatomical distribution of PTE was as follows : 1) left lung(n=103) < right lung(n=129), 2) upper and middle(or lingular) lobe(n=101) < lower lobe(n=116), 3) proximal < distal but 5th order in lower lobe was decreased in distribution. Spiral CT angiography could allow accurate demonstration of 19/20 cases(95%) PTE in our study. Spiral CT angiography could demonstrate acute PTE in 16 patients and chronic PTE in 3 patients. Spiral CT angiography could also showed the combined lung parenchymal lesions(Infarction(n=9 cases), atelectasis(n=4 cases), pleural effusion(n=6 cases)). CONCLUSIONS: Spiral CT angiography with 2D image (multiplanar reformation) and 3D images(shaded surface display, minimal intensity projection) is a noninvasive diagnostic tool in the pulmonary thromboembolism. This method had several advantages; 1) It was showed the distribution of pulmonary embolism in total lung field. 2) It had high sensitivity in diagnosis of pulmonary embolism. 3) It discriminated between acute and chronic PTE. 4) It was showed the associated disease such as lung infarction, atelectasis, pleural effusion. 5) It was correlated with scintigraphic findings.