In patients with lung cancer, decisions regarding treatment can depend on the diagnosis of hilar and mediastinal nodal involvement. We prospectively compared the diagnostic value of computed tomography (CT) with that of transtracheobronchial ultrasonography (TUS) in the evaluation of lymphadenopathy. Five patients with resectable lung cancer were studied. TUS was done with EU-M 20 or M 30 and lymph nodes located at #3, #4, #7, ipsilateral #10, and #11 were observed and measured. TUS findings, CT findings, and histological findings were evaluated and compared. The sizes of lymph nodes as measured by TUS were similar to or slightly smaller than their sizes as measured by CT. Hilar lymph nodes and lymph nodes located at right #4 were clearly observed with TUS, but were sometimes unclear with CT. Diagnosis of model involvement by TUS needs further study.