We evaluated the feasibility of σ measurable by EPT in evaluating lung and mediastinal mass lesions. EPT was performed in 21 patients with lung or mediastinal mass lesions. The lesion σ distribution, its relationship with histological findings, lesion size, location and the number of successful scans were evaluated. The malignant tumors had larger maximum σ and intralesional standard deviation and contrast. The larger the lesions, the greater were the intralesional contrast and entropy. The number of possible dynamic scans for reconstruction appeared to be larger in the upper lobe tumors, but the findings need to be confirmed with larger samples.