Lymph node metastasis is one of the important prognostic factors in the management of non-small cell lung cancer, and accurate lymph node staging is crucial to clinical diagnosis and management. However, due to limitations in sensitivity and specificity, imaging diagnosis does not detect all positive lymph node metastases, and therefore a proportion of stage N1 lymph nodes are pathologically confirmed postoperatively. In fact, it is difficult to detect microlymph node metastases preoperatively by imaging means. There is a lack of adequate understanding of the clinical prognosis of patients with stage N1 who are expected to have no lymph node metastases. To address this situation, Dr. SuminShin et al. from Sungkyunkwan University School of Medicine in Korea conducted a study, the results of which were published in the August 2, 2013 issue of AnnThoracSurg. The authors found that patients with unanticipated stage N1 non-small cell lung cancer had a better prognosis than patients expected to have N1 lymph node metastases. The study retrospectively analyzed patients with postoperative pathologically confirmed stage N1 non-small cell lung cancer from 2003 to 2009. A total of 305 patients were included in the study. All patients underwent preoperative CT and PET/CT examinations. 177 patients in the cN0 group had negative lymph node metastases by both CT and PET/CT, 68 patients in the cN0-1 group had negative CT examinations and positive PET/CT, and 60 patients in the cN1 group had positive examinations by both CT and PET/CT. The patients were statistically analyzed according to their clinical signs, imaging characteristics, pathological findings, postoperative results and recurrence and survival time. The results of the study showed that the cN1 group had larger tumors (p<0.001), higher T-stage (p=0.018), and a higher proportion of squamous carcinomas (p<0.001). Patients had a higher rate of positive N1 lymph nodes (p=0.004) and were more likely to have extra-envelope infiltration of lymph nodes (p<0.001). 5-year overall and disease-free survival was significantly lower in patients in the cN1 group (p=0.038, p=0.01), while there was no statistical difference between patients in the cN0 and cN0-1 groups (p=0.958, p=0.862). This study found that unanticipated stage N1 non-small cell lung cancer had a better prognosis and survival compared to patients with anticipated N1 lymph node metastasis, which is a guide for patients' surgery and adjuvant therapy.