This paper proposes a method for making correspondence between the supine and the prone positions of the colon in CT volumes. In CT colonography, two CT volumes in the supine and the prone positions are often taken to observe the whole colonic wall by comparing them. However, the colonic wall is soft and changes its shape when a patient changes positions. Therefore, physicians need to take the positional relations into account when comparing the two CT volumes. Calculation of the positional relations between the two positions of the colon can reduce load of physicians. A large number of haustral folds exists in the colon and the order doesn't change even when a patient change positions. Therefore, haustral folds are suitable for registering the supine and the prone positions of the colon. We also find sharply bending points of the centerline of the colon as landmarks for brief registration. The precise registration is then performed by finding positional correspondence of the haustral
folds in the supine and the prone positions. In correspondence search, we first find the correspondence among long haustral folds, followed by small haustral folds. As the result of experiment using six pairs of 3D abdominal CT volumes, 65.1% of the correspondence of large haustral folds were correct, 25.6% were incorrect, and 9.3%
could not be judged. On the other hand, 13.3% of the correspondence of small haustral folds were correct, 42.9% were incorrect, and 32.7% could not be judged.