As an evolving technique, linear endobronchial ultrasound is becoming the first choice and standard of care not only to diagnose the malignant and benign mediastinal lesions but also to stage non–small cell lung cancer. Lung cancer is the leading cause of cancer-related mortality in both men and women. The disease causes more death compared with colorectal, breast, and prostate cancers combined in the United States. Staging of lung cancer determines the prognosis. The type of lung cancer has changed in the past few decades. The frequency of adenocarcinoma has increased, whereas squamous cell carcinoma now is less frequent. Determining the cell type and its molecular characteristics allow targeted treatments in adenocarcinoma. The diagnosis of indeterminate mediastinal lymph nodes or masses and staging lung cancer might be challenging. This article will review the principles and clinical utility of endobronchial ultrasound in mediastinal lesions.