To evaluate diagnostic imaging of small lesions in the peripheral lung, three-dimensional (3D) reconstruction CT images were used to study 36 cases (including which had been 19 resected) of pulmonary nodules less than 3 cm in diameter. Rapid scanning was employed in 17 cases and helical scanning (in which the X-ray tube rotates continuously with simultaneous table sliding) in 19 cases. The rapid scanning could not be evaluated in two cases because respiratory motion resulted in discontinuous image data. We were able to evaluate 34 cases. The addition of 3D images to the conventional images made it possible for us to obtain useful information on visualizing relations between nodules and vascular structures in 32% (11/34) of the cases. The 3D images enabled us to visualize the lesions and pulmonary vessels three-dimensionally. It was, however, difficult to evaluate lesion shape since we were able to obtain useful information in only 3% (1/34) of the cases. In helical scanning, data are acquired from an extensive area within a short time, providing consecutive axial-slice images remain free of any respiratory artifacts. In this regard, helical scanning is suitable for generating 3D images. A diagnostic procedure based on 3D lesion analysis should be developed and standardized.