We find new obstructions on the topology of monotone Lagrangian submanifolds of C n under some hypothesis on the homology of their universal cover. In particular we show that nontrivial connected sums of manifolds of odd dimensions do not admit monotone Lagrangian embeddings into C n whereas some of these examples are known to admit usual Lagrangian embeddings: the question of the existence of a monotone embedding for a given Lagrangian in C n was open. In dimension three we get as a corollary that the only orientable Lagrangians in C 3 are products S 1 × Σ. The main ingredient of our proofs is the lifted Floer homology theory which we developed in [11].Mathematics subject classification : 57R17, 57R58, 57R70, 53D12.