Objective: To evaluate the results of the transthoracic biopsy of peripheral opacity in the lungs under a - Scan guidance. Subject and method: This study was conducted in the 198 Hospital from January 2013 to March 2014. Thirty-nine patients, whose chest conventional X - rays showed lung peripheral opacity but could not be diagnostically identified by bronchoscopy, were sent to undergo CT -guided transthoracic biopsy. Result and conclusion: The results showed 74.38 percent of the sample were at the age of more than 46 years old. Cytological diagnosis was affirmed in 31/39 patients (79.49 percent). The diseases were lung cancer (n=21, 53.85 percent), tuberculosis (n = 6, 15.38 percent), aspergilloma (n=2, 5.13 percent), and chronic inflammation (n=8, 20.51 percent). Complications occurred in 15.38 percent of the cases, which were pneumothorax (12.82 percent) and hemoptysis (2.56 percent). However, all events were mild and required medical treatment only.