To evaluate the potential role of dual energy CT (DECT) to visualize antiangiogenic treatment effects in patients with metastatic renal cell cancer (mRCC) while treated with tyrosine-kinase inhibitors (TKI). 26 patients with mRCC underwent baseline and follow-up single-phase abdominal contrast enhanced DECT scans. Scans were performed immediately before and 10 weeks after start of treatment with TKI. Virtual non-enhanced (VNE) and colour coded iodine images were generated. 44 metastases were measured at the two time points. Hounsfield unit (HU) values for VNE and iodine density (ID) as well as iodine content (IC) in mg/ml of tissue were derived. These values were compared to the venous phase DECT density (CTD) of the lesions. Values before and after treatment were compared using a paired Student's t test. Between baseline and follow up, mean CTD and DECT-derived ID both showed a significant reduction (p < 0.005). The relative reduction measured in percent was significantly greater for ID than for CTD (49.8 +/- 36,3 % vs. 29.5 +/- 20.8 %, p < 0.005). IC was also significantly reduced under antiangiogenic treatment (p < 0.0001). Dual energy CT-based quantification of iodine content of mRCC metastases allows for significantly more sensitive and reproducible detection of antiangiogenic treatment effects. aEuro cent A sign of tumour response to antiangiogenic treatment is reduced tumour perfusion. aEuro cent DECT allows visualizing iodine uptake, which serves as a marker for vascularization. aEuro cent More sensitive detection of antiangiogenic treatment effects in mRCC is possible.