Computed Tomograms of 45 patients with or without lung mass were reviewed to determine the characteristics ofthe major and minor fissures. Also pulmonary vascular distibutions were analyzed to localize each pulmonary lobe.The results were as follows; 1. Each major fissure area was imaged frequently as lucent band, less frequentlydense band. 2. The minor fissure areas were imaged as oval or triangular lucent zones. The oval or triangularlucent zones were as same frequency. 3. Avascular planes without above mentioned lucent zones were also correspondto minor fissure areas. 4. Slices of avascular zones wee observated between pulmonary arteries to posteriorsegment or apicoposterior segment of upper lobe and to superior segement of lower lobe on both lungs.