Dual-energy CT (DECT) is an innovative imaging technique that operates on the basic principle of application of two distinct energy settings that make the transition from CT attenuation-based imaging to material-specific or spectral imaging. The purpose of this review is to describe the use of DECT in oncology.Applications of DECT in clinical practice are based on two capabilities: material differentiation and material identification and quantification. The capability of obtaining different material-specific datasets (iodine map, virtual unenhanced, and monochromatic images) in the same acquisition can improve lesion detection and characterization. This approach can also affect evaluation of the response to therapy and detection of oncology-related disorders. DECT is an innovative imaging technique that can dramatically affect the care of oncologic patients.