Introduction: The platypnea-orthodeoxia syndrome (PO) includes: (i) a dyspnea increasing with orthostatism and decreasing in supine position, (ii) wide positional range in arterial oxygen saturation with tachycardia, (iii) and hypoxemia refractory to oxygen therapy. This syndrome is usually related to a cardiac right-left shunt, and rarely to a pulmonary shunt. Observation: We report a case of a patient presenting with a post-lung infection dyspnea associated with severe hypoxemia and shunt effect at blood gas. Contrast-enhanced CT-scan showed no pulmonary embolism. PO syndrome was suspected given the transcutaneous blood oxygen saturation variation from 90% in supine position to 60% in standing position, tachycardia, and absence of response to the intensive oxygen therapy. Conclusion: This syndrome should be known by physicians as a possible differential diagnose for refractory dyspnea to oxygen since effective treatment is available.