Best Paper Award The original publication is available at http://www.springerlink.comThe problem of defining robot behaviors to completely address a large and complex set of situations is very challenging. We present an approach for robot’s action selection in the robot soccer domain using Case-Based Reasoning techniques. A case represents a snapshot of the game at time t and the actions the robot should perform in that situation. We basically focus our work on the retrieval and reuse steps of the system, presenting the similarity functions and a planning process to adapt the current problem to a case. We present first results of the performance of the system under simulation and the analysis of the parameters used in the approach.Partial funding by the Spanish Ministry of Education and Science project DPI2003- 05193-C02-02. Raquel Ros holds a scholarship from the Generalitat de Catalunya Government his research was partially sponsored by BBNT Solutions, LLC under contract no. FA8760-04-C-0002 with the US Air Force.Peer reviewed