Abstract Hemodynamic factors play important roles in the formation, progression and rupture of cerebral aneurysms, and the Wall Shear Stress (WSS) and Oscillatory Shear Index (OSI) on the aneurysms are considered to be correlated with their growth and rupture. In this article, two computational models based on patient-specific cerebral aneurysms with daughter saccule are constructed from 3D-RA image data, one is lateral aneurysm located in middle cerebral artery (CA1) and the other is terminal aneurysm located in anterior communicating artery (CA2), The corresponding models of the two aneurysms by removing daughter saccule are established in order to investigate the initiation and growth of the daughter saccule. The flow patterns and the distributions of hemodynamic factors in the two aneurysms before and after daughter saccule is removed are obtained by solving the governing equations with the commercial CFD software Ansys CFX11.0 under the non-Newtonian fluid assumption. By analyzing the flow patterns, it is concluded that the aneurysms with daughter saccules have more complex and unstable flow patterns and hence are prone to rupture. By comparing the distribution of OSI, a hypothesis that a high OSI causes the growth of the daughter saccule is presented.