It is difficult to diagnose clinically silent or mild emphysema. The efficacy of CT scans for the diagnosis of emphysema has attracted attention and comparisons have been made between CT images and the pathological grade of emphysema in resected lungs. With a view to determine to what extent high resolution CT images are accurate concerning the diagnosis of mild emphysema, we conducted an extensive comparative study on CT scores of emphysema, based on high resolution CT, the pathology score derived from the cut surface of the lung identical in its plane with that of the CT and destructive index (DI) which is said to be instrumental in representing the degree of deterioration of alveolar walls in the same regions of the lungs. In this study, 42 patients who underwent thoracotomy and their lung specimens including a solitary nodule of considerable size have been employed. The CT scores and pathology scores depend on the picture grading system developed by Thurlbeck and coworkers for the basis of counting. The findings were such that with 1 mm collimation, the CT scores ranged between 12 and 57 with a mean +/- SD of 22.1 +/- 9.6 (n = 35) while with 5 mm collimation, the CT scores ranged between 7 and 46 with a mean +/- SD of 16.5 +/- 8.3 (n = 33). The pathology scores stood at 10 to 57 with a mean +/- SD of 23.2 +/- 9.8 (n = 42).(ABSTRACT TRUNCATED AT 250 WORDS)