Résumé : Synchronous oligometastatic non-small cell lung cancer (NSCLC) definition varies from 1 metastasis in 1 organ (tumour-node-metastasis 8 [TNM8]), 1-3 metastases (European Society for Medical Oncology [ESMO]), ≤3 metastases (including mediastinal nodes [MLN]) after systemic treatment to 3-5 metastases in ongoing trials. A single definition is however needed to design/compare trials. To assess oligometastatic NSCLC definitions used by clinical experts in daily practice and its evolution, we redistributed a 2012 case-based survey (Dooms, the World Congress of Lung Cancer 2013).