The standard surgical treatment for early stage non-smallcell lung cancer (NSCLC) is lobectomy or pneumonectomy with systematic lymph node dissection (SND) (1,2). In 2006, the European Society of Thoracic Surgeons (ESTS) released guidelines for intraoperative lymph node staging in NSCLC, in which intraoperative procedures for lymph nodes were classified into five groups; selected lymph node biopsy, (systematic) sampling, lobe-specific lymph node dissection (L-SND), SND, and extended lymph node dissection; and it was recommended to provide SND in all cases of complete resection of NSCLC (3). SND was first reported by Cahan in 1960 (4). This technique is designed to provide precise information on nodal status, which is necessary for optimal postoperative treatment, and to achieve better local cancer control that subsequently improves postoperative survival. However, the influence of SND on local control and survival remains uncertain, even though its value for accurate histologic staging of nodal status is well accepted. In addition, some reports have shown that SND tends to require longer operative times and to increase perioperative complications, compared to other procedures (5-7). Thus, many surgeons tend to avoid SND and perform "less invasive" intraoperative treatment for lymph nodes (8).Based on this background, L-SND has attracted attention as a procedure in which some nodal stations are left untouched and unresected depending on the lobar location of the primary tumor. L-SND is designed based on characteristic mediastinal nodal metastasis patterns that occur for different primary tumor locations. In 1998, Okada et al. showed the characteristic skip N2 metastasis pattern (9), and in 1999, Asamura et al. reported characteristic patterns based on the primary tumor location (10). According to their report, tumors in the RUL and LUL tend to metastasize to the superior mediastinal lymph node station, whereas single-station metastasis to the subcarinal node is very rare; while tumors in the RLL or LLL show metastases to the subcarinal node and to the superior mediastinal or aortic node (10). However, Asamura et al. concluded that subcarinal node metastasis was the touchstone of mediastinal spread of RLL and LLL tumors because singlenode or single-station metastases were more common in the subcarinal station and the prognosis of RLL or LLL tumors with both subcarinal and superior mediastinal lymph node metastases was extremely poor, even if SND was performed. Further, a specific lymphatic spread pattern was not identified for RML tumors (10).Comparing L-SND with SND from nodal staging Editorial