Objective We aimed to analyze the angioarchitecture characters and changes after combined bypass surgery (CBS) in pediatric moyamoya disease. Methods We retrospectively analyzed our database of consecutive patients with moyamoya angiopathy who received treatment. Only pediatric MMD cases aged between 3 to 19 years old whose pre- and post-operative imaging examinations including digital subtraction angiography and magnetic resonance imaging were enrolled in this study. The main trunk vessels stenosis and the collaterals from superficial-meningeal system and deep parenchymal system were evaluated before and after CBS. Results During short term follow-up period after the unilateral CBS, the stenosis of main trunk vessels both in operative (5.72.1 vs 6.81.8; P<0.001) and non-operative hemisphere (non-operative side 4.31.9 vs 5.72.1; P<0.001) progressed obviously. During the median follow-up period of 28.5 months after CBS, the decreasing of PCA-MCA anastomoses was much more significant (26 vs 6, P<0.001) than that of the PCA-ACA anastomoses (18 vs 19, P=0.807). Meanwhile, the subependymal anastomotic network could be relieved obviously (27 vs 2, P<0.001), while the inner thalamic and striatal anastomotic network had no significant change (31 vs 25, P=0.109). Conclusions The successful CBS could decrease the collaterals from PCA-MCA leptomeningeal system and the subependymal compensations in deep parenchyma significantly, while the main trunk stenosis would aggravate rapidly both in operative and non-operative hemisphere in short term after unilateral CBS. Therefore, strict and regular follow-up for the changes of vascular architecture and prompt surgical intervention for contralateral side might of benefit to pediatric MMD.Thieme. All rights reserved.