The paper reports on the etiopathogenetic aspects of mediastinitis, clinical and radiological semeiology, the latter with a decisive role in establishing the diagnosis. The priority character of therapy is emphasized. Three cases of mediastinitis in children are presented: a mediastinal abscess, a suppurated mediastinitis with favourable evolution after drainage and a mediastinitis secondary to a fistula on a postcaustic stenosed esophagus.