We provide data on neurophysiology and ultrasound of phrenic nerve. In the visualization of the phrenic nerve the main role is played by ultrasound. Conduction study of the phrenic nerve, if performed properly, is a simple and reliable method. In pediatric population, though, age dynamic and wide range of normative parameters has to be taken into the consideration. Ultrasound of the phrenic nerve allows visualization of the anatomical continuity of the nerve trunk of the nerve at the level of the neck and objectively assess the thickness of the nerve, which provides additional information to the doctor in clinical practice.