  We apply Hilbert module methods to show that normal completely positive maps
admit weak tensor dilations. Appealing to a duality between weak tensor
dilations and extensions of CP-maps, we get an existence proof for certain
extensions. We point out that this duality is part of a far reaching duality
between a von Neumann bimodule and its commutant in which also other dualities,
known and new, find their natural common place.
