Congenital and acquired abnormalities of the azygos vein can affect its size and position. Alteration of contrast material flow dynamics of the azygos vein on computed tomography can be an indication of superior vena cava obstruction. Recognition and accurate characterization of abnormalities of the azygos vein on imaging studies is critical to facilitate prompt diagnosis and direct workup when necessary. The main purpose of this article is to illustrate and describe the radiologic features of various congenital and acquired abnormalities affecting the azygos venous system.