Abstract Objective This study aimed to prove if pulmonary artery size influences survival and if an additional aortopulmonary shunt promotes left pulmonary artery growth after bidirectional cavopulmonary shunt in patients with hypoplastic left heart syndrome. Methods The medical records of patients with hypoplastic left heart syndrome who underwent Norwood procedure and bidirectional cavopulmonary shunt between 2007 and 2020 were reviewed. Right, left, and total (right + left) pulmonary artery indices were calculated according to Nakata and colleagues. Results A total of 158 patients were included in this study. Median age at Norwood and bidirectional cavopulmonary shunt was 8 (7-11) days and 3.6 (3.1-4.6) months, respectively. There were 7 hospital deaths and 12 late deaths. Survival after bidirectional cavopulmonary shunt was 90.3% at 1 year, and 86.2% at 2 years. Total, right, and left pulmonary artery indices were 238 (195-316), 136 (101-185), and 102 (75-130) mm2/m2 at the time of bidirectional cavopulmonary shunt, and they were 237 (198-284), 151 (123-186), and 86 (69-108) mm2/m2 at the time of Fontan. Left pulmonary artery index decreased significantly between the time of bidirectional cavopulmonary shunt and Fontan (p < 0.01). Nine patients needed partial takedown and additional aortopulmonary shunt due to failing bidirectional cavopulmonary shunt, but the additional aortopulmonary shunt did not promote the pulmonary artery growth significantly. Conclusions Preoperative pulmonary artery index did not affect the mortality after bidirectional cavopulmonary shunt. The partial takedown and additional aortopulmonary shunt for failing bidirectional cavopulmonary shunt were unable to improve left pulmonary artery size.