Abstract: Objective The purpose of this study is to describe and analyze the CT appearance of lung neoplasms after treatment with radiofrequency ablation (RFA).Methods The imaging of 233 pulmonary lessions treated by RFA in 226 patients with thoracicneoplasms were followed up. Two hundred and one neoplasms were primary lung cancer and 25 were metastases. The mean pretreatment neoplasm size was (4.36±2.45)cm (range, 1.00-10.60cm). The mean time of follow-up was 13.61 months (range, 1-30months). Imaging findings on CT were evaluated by three radiologists and thoracic surgeons by consensus.Results The most common finding immediately after treatment was peripheral ground-glass opacity surrounding the treated neoplasm, seen in 215 patients (95.13%,215/226). This lesion rapidly resolved by the end of the first month. 127 tumors (56.19%,127/226) developed bubble lucencies after ablation. Cavitation was seen in 51 tumors (22.57%,51/226) on follow-up CT and was more common in the bigger neoplasms. Malignant pleural effusions were usually seen after 3 months. One hundred and twenty-one tumors (65.05%,121/186) enlarged from pretreatment CT scans with follow-up imaging at 1 month. At 3 and 6 months after RFA, 66 cases (46.15%,66/143) and 57 cases (50.89%,57/112) tumors decreased in size. Then the percentage became to drop.Conclusion Conclusion peripheral ground-glass opacity, cavitation, and bubble lucencies are common findings on CT after RFA. Cavitation was more common in bigger neoplasms. Many treated neoplasms increased in size from baseline within 1 month. At 6 month, they decreased in size most obviously. Enlargement of a treated tumor after 6 months is regarded as tumor progression. CT scan is one of the effective methods to evaluate the lung neoplasm after RFA.