A 13-year-old girl presented with clinical features of pulmonary stenosis and regurgitation. Haemodynamic studies suggested the presence of a right ventricular tumour. M-mode and two dimensional echocardiograms indicated one or probably two soft thin walled structures originating from the right atrium. At operation a persistent right sinus venosus valve was removed. One earlier case report described the M-mode echocardiographic features of this condition in a neonate who died shortly after operation. This report illustrates that a large persistent right sinus venosus valve may present clinically years after birth. Echocardiography played an important role in making the diagnosis.