Abstract: Ojbective: To investigate the characteristics of mediastinal lymph nodes metastsis in T1 pulmonary squamous carcinoma and adenocarcinoma.Methods: 162 patients with T1 pulmonary carcinoma who underwent pulmonary resection plus system dissection of mediastinal lymph nodes were retrospectively analysized according to the mapping system developed by Naruke.Results: Of 162 patients,22 had mediastinal lymph nodes metastasized.Metastatic rate of N2 was 13.6%（22/162）.N2 metastatic rates in T1 pulmonary carcinoma with maximum diameter less than 1.5cm and between 1.6cm～3.0cm were 2.8% and 22.2% retrospectively,and no N2 metastatic lymph node was found in group with maximum diameter less than 1.5cm.N2 metastatic rates in groups of squamous carcinoma and adenocarcinoma were 5.6% and 20% respectively,the difference being significant.N2 metastatic rates in groups of well-differentiated and poorly differentiated were 4.3% and 23.2% respectively,the difference being significant.Conclusion: In T1 pulmonary carcinomas,N2 metastatic rate is closely related with the tumor diameter,the degree of differentiation,the pathological type.It is necessary to perform systematic mediastinal lymphadenectomy during pulmonary resection for those patients.