We prove an analogue for holonomic DQ-modules of the codimension-three conjecture for microdifferential modules recently proved by Kashiwara and Vilonen. Our result states that any holonomic DQ-module having a lattice extends uniquely beyond an analytic subset of codimension equal to or larger than three in a Lagrangian subvariety containing the support of the DQ-module.The author was supported by the EPSRC grant EP/G007632/1. 1 If codim S ≥ 3, is it true that any locally free (or even only reflexive) sheaf on X − S is extendable ?bundle of a complex manifold. It was recently proved by Kashiwara and Vilonen (see [14]). Theorem 1.2 ([14, Theorem 1.2]). Let X be a complex manifold, U an open subset of T * X, Λ a closed Lagrangian analytic subset of U, and Y a closed analytic subset of Λ such that codim Λ Y ≥ 3. Let E X the sheaf of microdifferential operators on T * X and M be a holonomic (E X | U \Y )-module whose support is contained in Λ \ Y . Assume that M possesses an (E X (0)| U \Y )-lattice. Then M extends uniquely to a holonomic module defined on U whose support is contained in Λ.The proof of the conjecture was made possible by the deep result of Kashiwara and Vilonen extending Theorem 1.1 to coherent sheavesDQ-modules in terms of perverse sheaves is not yet clear since the analogue of microlocal perverse sheaves is not known for DQ-modules. It is an interesting problem to define such objects.Here are the precise statements of the results we are proving.Theorem 1.4. Let X be a complex manifold endowed with a DQalgebroid stack A X such that the associated Poisson structure is symplectic. Let Λ be a closed Lagrangian analytic subset of X and Y a closed analytic subset of Λ such that codim Λ Y ≥ 3. Let M be a holonomic (A loc X | X\Y )-module, whose support is contained in Λ \ Y . Assume that M has an A X | X\Y -lattice. Then M extends uniquely to a holonomic module defined on X whose support is contained in Λ. and Theorem 1.5. Let X be a complex manifold endowed with a DQalgebroid stack A X such that the associated Poisson structure is symplectic. Let Λ be a closed Lagrangian analytic subset of X and Y a closed analytic subset of Λ such that codim Λ Y ≥ 2. Let M be a holonomic A loc X -module whose support is contained in Λ and let M 1 be an A loc X | X\Y -submodule of M| X\Y . Then M 1 extends uniquely to a holonomic A loc X -submodule of M. We hope that the submodule version of the codimension-three conjecture for DQ-modules may have applications to the representation theory of Cherednik algebras, via the localization theorem due to Kashiwara and Rouquier (see [10]).Let us describe briefly the proof of the above statements. As we already remarked, we follow the general strategy of Kashiwara and Vilonen (see [14]). Keeping the notations of the theorems 1.4 and 1.5 and denoting by j : X \ Y → X the open embedding of X \ Y into X, the problem essentially amount to show that j * M and j * M 1 are coherent. This is a local question. By adapting a standard technique in several complex variables in [18] to the cas...