Although the frequency of haemoptysis in Eisenmenger's syndrome is well recognised, the high prevalence of pulmonary artery thrombus has been newly appreciated through the growing use of non-invasive imaging. Three patients with Eisenmenger's syndrome with haemoptysis are reported who underwent computed tomography pulmonary angiography and cardiovascular magnetic resonance. Each patient was found to have aneurysmal dilatation of the right pulmonary artery with large laminar thrombus. These cases illustrate a rising clinical problem in this special population-that is, how to treat and prevent large pulmonary artery thrombosis in the setting of haemoptysis. The authors discuss their approach to these cases and the known literature.