Sentinel node (SN) identification in patients with lung cancer is useful not only to minimize lymph node dissection, but also to target the best lymph nodes for intraoperative frozen section during segmentectomy. Since 2000, we have identified the SN in lung cancer patients using radioisotope (RI). This review presents our data on SN identification, describing the following: the procedure, using a radioisotope tracer; the flow of Tc-99 tin colloid after the injection; the characteristics of patients whose SNs could not be identified; ex vivo SN identification; reliability of in vivo SN identification; the algorithm for reducing mediastinal lymph node dissection; the differences in SN identification between large and small radioisotope particles; SNs at segmental lymph nodes; SN navigation segmentectomy for clinical stage IA non-small cell lung cancer; and small metastasis in the SN.