Mediastinal masses are usually assessed by computer tomography (CT) and magnetic resonance imaging (MRI). Transthoracic ultrasonography (TUS) can also provide useful information concerning prevascular and posterior mediastinal masses abutting the thoracic wall, but is underused for mediastinal pathology. Moreover, it provides a valuable and safe method for guiding interventional procedures in those areas, even in cases when other approaches are difficult or impossible. Considering TUS a very useful imagistic method for diagnosing mediastinal masses, we present a pictorial essay of various mediastinal diseases which can be assessed by this method.