We present laser-induced thermotherapy (LITT) of primary and secondary lung tumors analysing indications and technical concepts. Thirty patients with lung metastases of different primary tumors (n=24) as well as localized lung tumors (n=6) were prospectively treated in 41 sessions using laser-induced thermotherapy (LITT). An MR-compatible puncture system was used with direct puncture technique. The puncture was performed via CT guidance in care vision technique. Eight patients were thermoablated using MR tomographical monitoring, 22 patients using CT monitoring. Local therapy effects, tumor control rate, side effects, complications, and survival were evaluated. In 74% of cases (28/38 lesions) of 24 patients with lung metastases and in all cases of the 6 patients with lung carcinoma a complete local ablation could be achieved. The complication rate (pneumothorax) was 9,8%. One patient with bronchial carcinoma had to be thoracotomized and resected. 93% of the patients are still alive. Percutaneous LITT of lung tumors permits a complete ablation of lung metastases and lung carcinomas with a low complication rate. Indications for the procedure were defined for patients with no more than 5 metastases up to 3 cm in size.