Most studies assessing the impact of bank mergers analyze the differential impact of these processes on a number of variables that characterize the banking system. However, this approach has important limitations, ignoring endogenous changes in market structure that might occur after the merger. This article analyzes the impact on credit markets of a number of bank mergers in the Portuguese banking system using this methodology usually employed in the literature, as well as an alternative methodology based on the estimation of a structural model, which allows for the derivation of a counterfactual scenario. In this framework it becomes possible to evaluate, using this structural model, what would have happened if the mergers had not occurred. We find that these mergers have contributed to a decrease in loan interest rates larger than what could have been anticipated. The flow of credit to non financial firms was larger than what was suggested by the combination of the pre-merger equilibrium with the post-merger environment. In contrast, the flow of loans to households was lower than expected, even though the loans granted to this sector have recorded a significant growth during the period analysed.