Portal hypertension causes serious and life-threatening complications. It is produced by increased resistance to blood flow through the portal axis, with a gradient to inferior vena cava higher than 5 mmHg. When this is 10 to 12 mmHg there is risk of bleeding from esophageal varices. In pediatric patients two different models exist: prehepatic (without liver disease), and intrahepatic (with liver disease), with different etiologies and prognosis. Doppler ultrasound, and liver function tests allow the distinction between them. Pediatricians should learn to recognize accurately the syndrome in order to approach the patients in a timely manner.