Improvements in CT technology have dramatically increased our ability to detect and diagnose liver abnormalities, particularly neoplastic disease. Because of the high prevalence of liver disease in patients referred for abdominal CT examinations, contrast administration and scanning techniques are usually optimized for detection of liver disease on abdominal CT scans. A wide variety of contrast techniques can be used to evaluate the liver, and it is important to understand both the rationale behind each technique and the impact on the quality of the examination when one deviates from these techniques. In addition, the timing of contrast administration and scan acquisition has become critical, and improper timing can cause lesions that are easily visualized to be obscured. This article reviews principles of lesion detection and the effects of various contrast techniques on lesion visualization.