Dual-energy computed tomography (DECT) can amply contribute to support oncological imaging: the DECT technique offers promising clinical applications in oncological imaging for tumour detection and characterisation while concurrently reducing the radiation dose. Fast image acquisition at two different X-ray energies enables the determination of tissue- or material-specific features, the calculation of virtual unenhanced images and the quantification of contrast medium uptake; thus, tissue can be characterised and subsequently monitored for any changes during treatment. DECT is already widely used, but its potential in the context of oncological imaging has not been fully exploited yet. The technology is the subject of ongoing innovation and increasingly with respect to its clinical potential, particularly in oncology. This review highlights recent state-of-the-art DECT techniques with a strong emphasis on ongoing DECT developments relevant to oncologic imaging, and then focuses on clinical DECT applications, especially its prospective uses in areas of oncological imaging.

• Dual-energy CT (DECT) offers fast, robust, quantitative and functional whole-body imaging.

• DECT provides improved tumour detection and more detailed tissue differentiation and characterisation.

• DECT affords therapy monitoring with complementary information and reduced radiation dose.

• The use of DECT in oncology is of increasing clinical importance.

• The potential of DECT in oncology has not been fully exploited yet.