Pulmonary arterial hypertension (PAH) is a disease characterized by increased pulmonary vascular resistance and severe hypoxemia. The cause of PAH in children is very different compared to the etiology in adults; in children PAH can be idiopathic in a vast majority of cases or associated with congenital heart disease (CHD). PAH is a disease that demands early diagnosis and this is crucial for a better prognosis of the patient. Bosentan (BST) is the first and the only oral drug approved by the health authorities for the treatment of the disease. In addition, it is a drug with the highest level of evidence “A”, defined by the World Health Organization (WHO), for the treatment of PAH. Recent experience with BST in pediatric patients with PAH has shown that the drug offers a safe, effective and easy-to-administrate therapy. It is a specific and competitive antagonist of endothelin A (ETA) and endothelin B (ETB) receptors with high affinity for ETA. BST decreases the pulmonary and systemic vascular resistance, resulting in increased cardiac output without increasing heart rate. Furthermore, it has been observed that it is well tolerated and does not negatively affect systemic blood pressure or the liver transaminase levels. For the proper management of BST pharmacokinetics it is necessary to know the pharmacokinetic profile specifically in children, where dosage is a variable that determines pharmacological parameters and to consider the aspects that guarantee its efficacy and safety, which are the main points reviewed in this paper.