  We investigate the Wightman function, the mean field squared and the vacuum
expectation values of energy-momentum tensor for a scalar field in AdS
spacetime, in the presence of a brane perpendicular to the AdS boundary. On the
brane the field operator obeys Robin boundary condition. The vacuum expectation
values are decomposed into the boundary-free AdS and brane-induced
contributions. In this way, for points away from the brane, the renormalization
is reduced to the one in pure AdS spacetime. It is shown that at proper
distances from the brane larger than the AdS curvature radius the brane-induced
expectation values decay as power-law for both massless and massive scalars.
This behavior is in contrast to that for a plane boundary in Minkowski
spacetime, with an exponential decay for massive fields. For Robin boundary
conditions different from Dirichlet and Neumann ones, the brane-induced part in
the energy density is positive near the brane and negative at large distances.
For Dirichlet/Neumann boundary condition the corresponding energy density is
negative/positive everywhere. We show that, for a fixed value of the proper
distance from the brane, near the AdS boundary, the Neumann boundary condition
is an "attractor" in the general class of Robin boundary conditions, whereas
Dirichlet boundary condition is an "attractor" near the horizon.
