In this paper, we are interested in aggregated search in structured XML documents. We present a structured information retrieval model based on possibilistic networks. Relations terms-elements and elements-document are modeled through possibility and necessity. In this model, the user's query starts a process of propagation to recover the elements. Thus, instead of retrieving a list of elements that are likely to answer partially the user's query, our objective is to build a virtual elements that contain relevant and non-redundant elements, that are likely to answer better the query that elements taken separately. Indeed, the possibilistic network structure provides a natural representation of links between a document, its elements and its content, and allows an automatic selection of relevant and non-redundant elements. We evaluated our approach using a sub-collection of INEX (INitiative for the Evaluation of XML retrieval) and presented some results for evaluating the impact of the aggregation approach.