A comparison between the observed averaged vertical profile of NGC 891 in the I band (solid line) and the corresponding model predictions (dashed line) for three cases: the one dust disk model (left panel) with and one stellar disk (the old stellar disk); the two dust-disk model (middle panel) with and one stellar disk (the old stellar disk); the two dust-disk model (right panel) with and two stellar disks (the old and the young stellar disk).