Obesity is a morbid condition with hemodynamic consequences affecting the systemic and pulmonary circulations leading to a risk of pulmonary hypertension. Data in the literature do not argue in favor of a direct relationship between pulmonary hypertension and obesity. These two conditions appear to be two distinct entities, the different co-morbidities observed in obesity favoring pulmonary hypertension. Certain co-morbidities, for instance use of anorexic agents, exhibit a clear relationship with pulmonary hypertension. There is also a possible relationship with left ventricular failure, hypoxemia, and other respiratory disorders (including obstructive sleep apnea), hypothyroidism, and thomboembolism.