Hemodynamics　are　thought　to　play　an　important　role　in　the　creation,　thrombosis,　recanalization,　regrowth　and　re-bleeding　of　cerebral　aneurysms　treated　by　endovascular　means.　Recently,　the　stents　for　cerebral　aneurysms　are　expected　to　be　flexible　enough　to　prevent　injuries　in　small　diameters　and　intricate　vessels.　And　the　lattice　Boltzmann　method　has　received　considerable　interest　as　an　efficient　method　of　computing　a　variety　of　fluid　flows,　especially　with　complex　geometrical　configurations.　Therefore,　2-dimensional　mathematical　model　of　cerebral　aneurysm　with　stent　were　created.　Furthermore,　CFD　calculations　were　performed　by　using　lattice　BGK　model　with　the　assumption　of　Newtonian　fluid　property　for　blood　and　the　rigid　wall　property　for　the　vessel　and　the　aneurysm.　The　results　suggest　that　stent　prevents　vortices　driven　directly　by　the　parent　vessel　flow　and　that　the　ratio　of　the　stent　pore　size　to　the　aneurysm　orifice　size　plays　an　important　role　in　the　formation　of　stented　flow　pattern,　and　small　pore　size　is　preferable　for　the　aneurysm　with　large　orifice　though　it　causes　a　kind　of　orifice　effect　and　prevents　the　flow　reduction　in　the　stented　aneurysm　with　small　orifice.　©　2008　Springer-Verlag.