Primary heart tumours are rare with an incidence of 0.02% in reported autopsy series. One of the most uncommon is haemangioma. We describe the case of a 51-year-old woman, who presented with a giant cavernous haemangioma, but with no clinical manifestations other than atrial fibrillation. Performed echocardiography showed a giant (6.5 x 7.5 cm) tumour located in the right atrium, modelling other heart chambers. In order to improve atrial haemodynamics, a large portion of the tumour was removed via sternotomy. Examination after 12 months showed no further growth of the unremoved part of the tumour.