The current procedure used to check for cancer cells in the lungs is a small operation at the base of the neck (mediastinoscopy) to get samples of the lymph glands. These samples are then looked at under the microscope to see if they contain cancer cells. A procedure has been developed that may allow doctors to get samples of lymph glands without having to perform an operation. This is called endobronchial ultrasound or "EBUS". The purpose of this study is to compare the 2 procedures.