The authors report two cases of coronary-right ventricular fistulas diagnosed in a 7-month-old infant and a 9-year-old girl. The discovery of the heart disease was incidental in both cases, following detection of a low continuous murmur. Doppler ultrasonography established the diagnosis, which was confirmed by haemodynamic studies and coronary angiography. The left anterior descending artery was involved in both cases and the recipient cavity was the right ventricle. The first patient was cured by early operation with distal ligation of the artery. In the second patient, the natural course was complicated by aneurysmal dilatation of the coronary artery. The authors recall the value of colour Doppler ultrasound in the noninvasive diagnosis, especially of the recipient cavity by colour Doppler and the need to rapidly treat coronary fistulas to prevent the development of complications reported after an average age of 20 years.