Iodine uptake in the lungs and intrathoracic lesions on postcontrast dual-energy computed tomography is used for evaluation of pulmonary embolism-related perfusion defects and pulmonary infarctions. It has been applied in characterization and treatment response assessment of lung and mediastinal abnormalities. We report a new imaging artifact or faulty image postprocessing in a commercially available rapid kV switching technique of dual-energy computed tomography, which can confound its clinical utility for evaluation of iodine uptake.