Objective. To evaluate the effectiveness of CT-guided thoracic biopsy in the diagnosis of lung and mediastinal malignancies.Materials and methods. A retrospective analysis of 32 cases of CT-guided transthoracic biopsy was performed. Lung and mediastinal masses suspicious for malignancy with a size of more than 2.0 cm in the area available for manipulation were the indication for Cor-biopsy with additional examination of impression smears. A step-by-step procedure involved CT positioning of the object, marking by the radiation therapy program, and performing the procedure. The cytological and histological materials were evaluated and compared.Results. The analysis of manipulations performed in 32 patients with lung masses (75±7.7%) and mediastinal masses (25±7.7%) proved the technical effectiveness of the procedure, which lasted 37±9 minutes. The diagnosis was confirmed by cytological analysis of impression smears in 81.3±6.9% of cases, and using histological methods – in 71.9±8% (p>0.05). The agreement between the results obtained by both methods was 53.1±8.8%. Immunohistochemical analysis of the material was performed in 69.6±9.6% of patients. Procedural complications (pneumothorax and hemoptysis) were observed in 21.9±7.3% of patients. Cytological examination allowed the results of a planned histological and immunohistochemical analysis to be foreseen with a high degree of probability.Conclusion. CT-guided transthoracic puncture is a highly effective method of diagnosing lung and mediastinal malignancies, which allows their morphological characterization to be done in 81% of cases.