AIM OF THE STUDY: To prove in vivo and on cadaveric lungs, the constancy of the collateral type of distribution for the right and left pulmonary arteries as described in classical books and modern studies; to estimate the frequency of the main branches observed and define an arterial tree of reference set up with the most common branches for reading the CT pulmonary angiographies. PATIENTS AND METHODS: Sixty three-dimensional reconstructions of pulmonary arterial trees (right: 30; left: 30) using the Volume Rendering Technique (VRT) performed from CT angiographic studies of 30 patients without bronchial, arterial or pulmonary pathology. Dissection of 16 pulmonary arteries from eight fresh cadavers injected with latex. Finally, 76 pulmonary arteries (right: 38; left: 38) were examined. RESULTS: The most common division of the pulmonary artery is a collateral distribution but in seven cases from 38 (18.4%) at right and one case from 38 (2.6%) at left the artery ended in two or three terminal lobar trunks which provided the segmental arteries. The mediastinal artery for the upper right lobe was always found, with a complementary scissural artery in 89.5% of cases; a middle lobar trunk was observed in 22 of the 38 right lungs (57.9%). On the left tree, four different but usually not coexisting mediastinal arteries were identified for the upper lobe, three for the culmen and one for the lingula; six various scissural arteries were noted, three for the culmen and three for the lingula; the segment 6 received one or two segmental arteries, exceptionally three. An arterial tree of reference could be defined for both sides. CONCLUSION: The division in terminal lobar trunks of the pulmonary arteries is a variation demonstrated for the first time. The data obtained from 3D reconstruction imaging in vivo are in conformity with the results of studies performed on injected cadaveric lungs for this point and to define the arterial tree of reference.