The following Bernstein-type theorem in hyperbolic spaces is proved. Let Si
gma be a non-zero constant mean curvature complete hypersurface in the hype
rbolic space H-n. Suppose that there exists a one-to-one orthogonal project
ion from Sigma into a horosphere. (1) If the projection is surjective, then
Sigma is a horosphere. (2) If the projection is not surjective and its ima
ge is simply connected, then Sigma is a hypersphere.