Patent foramen ovale (PFO) has a prevalence of 25%-27% in the general population  and it has been suggested to be the mediator for a wide variety of syndromes based on the paradoxical embolism. The obstructive sleep apnea syndrome (OSAS) is a common disorder in the middle-aged population. An echocardiographically visible PFO was detected in 27%-69% of patients with documented OSAS suggesting a relationship between PFO and OSAS, but the pathophysiology of this potential relationship is still unclear. It has been shown that obstructive apnea can induce right-to-left shunting (RLS) through PFO with two proposed mechanisms including a large swing in pleural pressure and pulmonary hypertension. Pulmonary artery hypertension and oxygen desaturation have been suggested to be caused by the concurrence of OSAS and PFO. Arguments against and in favour of this potential relationship are discussed in this brief review.