In this paper, we introduce an information theoretic method for estimating the usefulness of the hyperlink structure induced from the set of retrieved documents. We evaluate the effectiveness of this method in the context of an optimal Bayesian decision mechanism, which selects the most appropriate retrieval approaches on a perquery basis for two TREC tasks. The estimation of the hyperlink structure’s usefulness is stable when we use different weighting schemes, or when we employ sampling of documents to reduce the computational overhead. Next, we evaluate the effectiveness of the hyperlink structure’s usefulness in a realistic setting, by setting the thresholds of a decision mechanism automatically. Our results show that improvements over the baselines are obtained. Categories and Subject Descriptors H.3.3 [Information Storage and Retrieval]: Information Search and Retrieval General Terms Experimentation, Algorithms, Theory Keywords Web information retrieval, Bayesian decision th...