Endovascular　coiling　is　the　predominant　method　for　treating　cerebral　aneurysms.　Extensive　reports　on　selecting　coil　length,　hardness,　and　material　are　available.　However,　the　impact　of　coil　diameter　on　postoperative　outcomes　remains　unclear.　This　study　enrolled　six　personalized　geometric　models　of　intracranial　aneurysms:　three　bifurcation　aneurysms　and　three　sidewall　aneurysms.　Four　coil　models　were　constructed　by　changing　the　coil　diameter.　Coil　embolization　was　simulated　using　the　finite　element　method.　Computational　fluid　dynamics　was　used　to　characterize　hemodynamics　in　the　aneurysms　after　embolization.　Evaluation　parameters　included　velocity　reduction,　wall　shear　stress　(WSS),　low　WSS　(LWSS),　oscillatory　shear　index　(OSI),　relative　residence　time　(RRT),　and　residual　flow　volume　in　the　aneurysms.　At　the　peak　time　(t　=　0.17　s),　the　proportion　of　LWSS　area　in　bifurcation　aneurysms　increase　with　the　rise　in　coil　diameter:　0.8D,　71.28　±　12.62%　versus　1D,　74.97　±　19.17%　versus　1.2D,　78.88　±　18.56%　versus　1.4D,　84.00　±　11.53%　(mean　±　SD).　The　proportion　of　high　OSI　area　decreases　as　the　coil　diameter　increases:　0.8D,　4.41%　±　2.82%　versus　1.0D,　3.78　±　3.33%　versus　1.2D,　2.28%　±　1.77%　versus　1.4D,　1.58%　±　1.11%　(mean　±　SD).　The　proportion　of　high　RRT　area　increases　as　the　coil　diameter　rises:　0.8D,　3.40%　±　1.68%　versus　1.0D,　7.67　±　4.12%　versus　1.2D,　9.84%　±　9.50%　versus　1.4D,　22.29%　±　14.28%　(mean　±　SD).　Side　wall　aneurysms　do　not　exhibit　the　aforementioned　trend.　Bifurcation　aneurysms　plugged　with　a　coil　of　1.4　times　the　diameter　have　the　largest　RFVs　(＜10　mm/s)　within　the　group.　Aforementioned　patterns　are　not　found　in　sidewall　aneurysms.　In　the　treatment　of　aneurysms　with　coiling,　varying　coil　diameters　can　result　in　different　hemodynamic　environments　within　the　aneurysm.　Larger　coil　diameters　have　improved　hemodynamic　performance　for　bifurcation　aneurysms.　However,　coil　diameter　and　embolization　effectiveness　have　no　significant　relationship　for　sidewall　aneurysms.　©　2024　John　Wiley　&　Sons　Ltd.