In recent years, many studies have proven that percutaneous thermal ablation is an effective second-line treatment method with low complication rates in early-stage non-small cell lung carcinoma and lung metastases. Radiofrequency ablation and microwave ablation are commonly used for this purpose. To evaluate the factors affecting the success of the percutaneous thermal ablation treatment with technical success, complication rates, and long-term follow-up results in metastatic lung lesions. Computed tomography (CT)-guided percutaneous ablation was performed for 70 metastatic lung lesions in 35 patients (22 men, 13 women; mean age = 61.34 years; age range = 41-75 years). Radiofrequency ablation was performed in 53/70 (75.7%) lesions and microwave ablation in 17/70 (24.3%) lesions. The technical success rate was 98.6%. Median overall survival, progression-free survival, and local recurrence-free survival of the patients were 33.9 months (range=25.6-42.1 months), 12 months (range=4.9-19.2 months), and 24.2 months (range=8.2-40.1 months), respectively. One- and two-year overall survival rates were 84% and 74%, respectively. Median progression-free survival times were 20.3 months and 11.4 months, respectively, according to the number of metastatic lung lesions being single and multiple, and the difference was statistically significant (P = 0.046). According to the number of lesions ≤3 and >3, the difference was also found statistically significant (P = 0.024) (14.3 months and 5.7 months, respectively). In conclusion, CT-guided percutaneous thermal ablation is a safe and effective treatment method in metastatic lung lesions. The number of lesions is the most important factor in predicting treatment success.