to compare packing, reopening and retreatment of intracranial aneurysms treated with two types of coils with different wire thickness and different shapes. Packing, defined as ratio between volume of inserted coils and volume of aneurysm, was calculated for 235 aneurysms, 120 treated with predominantly helical shaped coils of 0.010 inch wire diameter (GDC 10) and 115 treated with predominantly complex shaped coils of 0.012 inch wire diameter (Cordis TruFill). Aneurysm packing, reopening and retreatment during follow up were compared for aneurysms treated with either type of coils. Mean packing was significantly higher (absolute value 6.8 %, relative value 23.0 %, P<0.0001) in aneurysms treated with Cordis TruFill coils compared to aneurysms coiled with GDC 10 coils. Six months follow up angiography was available in 194 of 235 aneurysms. Reopening occurred in 22 of 99 aneurysms (22.2%) treated with GDC 10 coils and in 15 of 95 aneurysms (15.8%) treated with Cordis TruFill coils. Retreatment was performed in 16 of 120 aneurysms (13.3%) treated with GDC 10 coils and in 9 of 115 aneurysms (7.8%) treated with Cordis TruFill coils. Using complex shaped Cordis TruFill coils with a wire diameter of 0.012 inch to coil intracranial aneurysms results in significantly better packing compared to helical GDC 10 coils of 0.010 inch wire diameter. Retreatment rate was lower for aneurysms treated with Cordis TruFill coils compared to aneurysms treated with GDC 10 coils.