Objective To investigate the differences in energy spectrum CT findings between anterior mediastinal lymphoma and thymic carcinoma. Methods Twenty-two cases of anterior mediastinal lymphoma and 28 cases of thymic carcinoma confirmed by biopsy in Tangshan People's Hospital were selected.The CT values and changes of iodine content and water content in lesion sites were measured by energy spectrum analysis software.The differences between anterior mediastinal lymphoma and thymic carcinoma were compared. Results The single-energy CT value of 40-80 keV in thymus carcinoma was higher than that in anterior mediastinal lymphoma( P =0.001, P =0.037, P =0.042, P =0.034, P =0.002; P =0.016, P =0.013, P =0.018, P =0.024, P =0.012).The difference in the single-energy CT value of 90-110 keV between anterior mediastinal lymphoma and thymic carcinoma showed no statistical significance(all P >0.05).The concentrations of water in the arterial and venous stages of thymic carcinoma were significantly lower than those in the anterior mediastinal lymphoma( P =0.030, P =0.037),whereas the iodine concentrations were significantly higher( P =0.026, P =0.000). Conclusion Anterior mediastinal lymphoma and thymic carcinoma have remarkably different 40-80 keV single energy CT value and iodine concentration in arterial and venous phases,which may be helpful for the differential diagnosis of these two malignancies.