Primary cardiac tumours are rare; their prevalence ranges from 0.0017% to 0.28% in various autopsy series. Cardiac lipomas are well-encapsulated benign tumours typically composed of mature fat cells, and their reported size ranges from 1 to 15 cm. They are usually seen in the left ventricle and the right atrium. Lipomas are true neoplasms, as opposed to lipomatous hypertrophy of the interatrial septum, which is a nonencapsulated hyperplastic accumulation of mature and foetal adipose tissue. Cardiac lipomas occur in patients of all ages, and the frequency of occurrence has been found to be equal in both sexes. Patients are usually asymptomatic, although the manifestation of symptoms depends upon both size and location of the tumour. We present the case of a patient with an interatrial septal lipoma, causing obstruction of the superior vena cava.