A 23-year-old female patient was referred for treatment of a posterior mediastinal tumour. There was no history of hypertension or headache and no other complaints. The patient's blood pressure increased to 210/125 mmHg after surgically manipulating the tumour, subsequently reversing to severe hypotension (25/15 mmHg) immediately after the tumour was removed. The life-threatening and irreversible blood pressure drop was difficult to treat with fluid and vasopressors, and the patient ultimately died of cardio-respiratory failure. Asymptomatic paraganglioma can be non-functional but can also be fatal. For any lump in the thoracic cavity, paraganglioma should be ruled out.