PURPOSE: To evaluate the frequency and degree of fusion of the lung, as seen on high-resolution CT(HRCT). MATERIALS AND METHODS: In 210 patients high-resolution CT scans from the apex to the diaphragm were obtained at 1mm collimation and 7mm interval. We retrospectively analysed the frequency and degree of fusion of the lung bordering each interlobar fissure. Fusion of the lung was defined when fissure appeared without complete lobar separation. The degree of lung fusion was classified as mild (less than 1/3 of the fissure), moderate (greater than 1/3 and less than 2/3 of fissure), or severe (greater than 2/3 of the fissure). RESULT: In 90 of 210 patients, all fissures were identified. In 73 of these 90 (81.1%), lung fusion was noted, the most frequent site of this being between the right upper and right middle lobe (53.3%). The least frequent site was between the upper portion of the left upper and left lower lobe (32.2%). Am mild degree of fusion was most frequently found between the right middle and right lower lobe (83.9%), while a severe degree was most frequentl between the right middle and right upper lobe (50.0%), followed by the lingular division and the left lower lobe (41.9% ). CONCLUSION: HRCT can be used to were able to evaluate the frequency and degree of interlobar lung fusion.