A retrospective study of 150 patients with suspected pulmonary embolism (PE) who underwent contrast-enhanced dual-layer DECT (dl-DECT) evaluated the performance of electron density and Z-effective maps derived from unenhanced dl-DECT images in detecting PE. Contrast-enhanced dl-DECT was used as the reference standard. The results revealed that the electron density map superimposed on the Z-efficacy map was able to identify the embolus with high accuracy, sensitivity, and specificity. Thus, contrast-free dl-DECT may help to investigate suspected pulmonary embolism in frail patients with severe contraindications to iodinated contrast media, such as kidney failure or allergies to contrast medium.