The objective of this comparative study is to determine the MDCT features of solitary pulmonary tuberculous cavity and malignant cavity and to analyze the advantages there-of in differential diagnosis. The clinical data and MDCT findings of 51 cases of pulmonary tuberculous cavities and 39 cases of malignant cavities were reviewed retrospectively, which include the general aspects of patients, the manifestation of cavity and the changes of adjacent structures. The results revealed that the tuberculous cavity tends to locate in the upper lobe or the superior segment of lower lobe, and it is usually acompanied with cavity wall calcification, satellite lesions, peripheral inflammation, lymph node calcification, small diameter and thin wall thickness. The malignant cavities, showing no disposition to locate in a lobe or segment, are characterized by mural nodules, off-center cavity, lobulation, coarse speculation, lymph node enlargement, vascular clustering sign, big diameter and thick wall. In conclusion, with multiplanar reconstruction on multi-detector row CT, we could elaborate the cavities and the accompained lesions, thus contributing to a correct diagnosis in most cases.