Background : Tumor size in lung cancer is not as good a prognostic factor for adenocarcinoma as it is for other types of lung cancer; therefore it is difficult to estimate the prognosis preoperative. However, there have recently been some reports on the radiologic findings correlating to the clinicopathologic prognostic factors in peripheral small adenocarcinoma of lung. We tried to evaluate the prognostic importance of High-Resolution CT (HRCT) findings of such adenoearcinoma, Material and Method: One houndred and seventy-six surgically resected small peripheral adenocarcinoma measuring 3 cm or less in greatest dimension were reviewed radiologically and clinicopathologically. Result: The patients with greater extent of ground-glass attenuation (GGA) had better clinico-pathological factors. The tumors with gross appearance of GGA or bubble-like shape showed better clinicopathological prognostic factors than scar-like or solid shape. Conclusion: HRCT findings of small peripheral adenocarcinomas of the lung correlated well with the histologic and clinical prognostic factors. We can predict the post-operative prognosis with the radiologic findings.