PLATYPNOEA orthodeoxia is a rare syndrome of postural hypoxaemia accompanied by breathlessness. The predominant symptom, dyspnoea induced by upright posture, can be debilitating and difficult to discern without thorough evaluation of the patient's pattern of dyspnoea. The precise cause of the syndrome is unclear but patients develop right to left intracardiac shunting in the presence of normal right sided cardiac pressures. Initially, patients should have confirmation of orthostatic desaturation by erect and supine pulse oximetry. However, definitive diagnosis of an orthostatic intracardiac shunt is most readily established by echocardiography. The use of echocontrast with postural manoeuvres may facilitate the diagnosis. The treatment of choice is surgical closure of the intracardiac (usually interatrial) communication, which may result in dramatic symptomatic and haemodynamic improvement. Three cases (a 27 year old man and two women aged 63 and 72 years) are described that exemplify the presentation of this syndrome, and reflect the varied management strategies and outcomes of this condition.