Spiral CT has been advocated as a major advancement in CT technology. Spiral CT scanning is rapid, the volume of IV contrast material can potentially be decreased, and high-quality coronal, sagittal, and three-dimensional reconstruction is possible. However, when compared with dynamic CT, because of the shorter acquisition time of spiral CT, vascular and organ enhancement on spiral CT scans is more dependent on factors that affect the delivery of contrast material into the bloodstream and on the time that scanning begins after the start of injection of contrast material. Additionally, organs other than the liver are scanned earlier than they typically are during a dynamic study, particularly the kidneys and spleen. In our experience to date, these aspects of spiral scanning have led to several difficulties in the interpretation of spiral CT scans. This essay illustrates potential pitfalls in the interpretation of spiral CT scans associated with scanning too soon after injection of contrast material.