Abstract. In this paper we study the performance of linguisticallymotivated conflation techniques for Information Retrieval in Spanish. In particular, we have studied the application of productive derivational morphology for single word term conflation and the extraction of syntactic dependency pairs for multi-word term conflation. These techniques have been tested on several search engines implementing different indexing models. The aim of this study is to find the strong and weak points of each technique in order to develop heuristics for automatic query expansion.