Severe obesity can produce a marked impairment of respiratory function. The obesity hypoventilation or Pickwickian syndrome comprises of extreme obesity, alveolar hypoventilation, somnolence, plethora, pulmonary hypertension and right heart failure. It is sometimes associated with obstructive sleep apnea but can be distinguished from obstructive sleep apnea by the presence of awake CO2 retention. Alt hough uncommon, it is important to recognize this syndrome because due to its potential life threatening nature and because can be reversed by appropriate treatment. Here, we report 3 cases of obesity hypoventilation syndrome.