Haematogenous lung metastases are usually considered a sign of widespread metastatic disease. However, in most primary cancers, the first filter for distant tumours are the lungs. In some patients, the metastatic process may stop at the lungs. In these selected patients, there are studies that have shown the benefits of metastasectomy. The objective of this paper is to analyse the morbidity and mortality of lung metastasectomy and determine the factors that predispose to early relapse. Forty-two patients operated on for lung metastases, and four were excluded as they were assessed intraoperatively to be unresectable, leaving 38 patients to be analysed. The variables analysed were: age, sex, primary tumour, disease-free interval, number of metastases, bilaterality, morbidity and mortality, relapse, reinterventions, relapse-free interval after metastasectomy and survival. The surgical technique was a posterolateral thoracotomy, and there were no perioperative deaths. Morbidity was 11% (n = 4), and surgical reintervention of the haemothorax was necessary. Survival after 1, 2 or 3 years was 87%, 61% and 25% respectively, and the percentage of relapse-free patients was 71%, 56% and 17% respectively. The main factors associated with early relapse were histological type of tumour (more relapse in sarcoma, and less in adenocarcinoma), the disease-free interval between the primary tumour and lung metastases, and the number of metastases. Surgery was required a second time in five patients who had relapsed lung metastases, but extirpation could be performed in only four patients, of whom three were relapse free after 6, 12 and 24 months respectively, and the fourth had relapsed lung metastases after 18 months. Resection of lung metastases can be performed with low morbidity and mortality. The main prognostic factors for survival are complete surgery, histological type, disease-free interval between the primary tumour and metastases, and the number of lung metastases.