Free Data Structures are finite semantic trees modulo equational axioms that are useful to represent classical data structures such as lists, multisets and sets. We study the satisfiability problem when free data structures are combined with bridging functions. We discuss the possibility to get a combination methodàmethod`methodà la Nelson-Oppen for these particular non-disjoint unions of theories. In order to handle satisfiability problems with disequalities, we investigate a form of sufficient surjectivity for the bridging functions.