Frontal cardiac area, right descending pulmonary arterial size and size of the ductus arteriosus were measured on 29 patients with patent ductus arteriosus, 21 females and 8 males. The results are as follows: 1. Frontal cardiac area in PDA patient in this series is increased in 0.63% to 100.11% and the average is 38.91 - 23.54%. 2. Central branch of the right descending pulmonary artery is dilated in 28 cases (96.55%) on pre-operative stage, and combination with dilation of central branch and constriction of peripheral branch is in 18 cases (62.1%). 3. Degree of dilation of central branch is correlated with increase of age, but it is not related with size of ductus arteriosus. 4. Increase rate of frontal cardiac area is not related with size of ductus arteriosus.