The subject of the paper is representations of Hilbert C * -modules. We introduce the concept of a nondegenerate, irreducible and cyclic representation and the commutant of a Hilbert C * -module. Relations between representations of a Hilbert C *module, its linking algebra and underlying C * -algebras are discussed. We also study Hilbert CCR-and GCR-modules and extend some results from CCR-and GCRalgebras. The results we obtain are similar to the results known for C