The paper presents the results of a two years outdoor monitoring campaign that has been carried out on the same polycrystalline photovoltaic module at two different locations in Europe: the SUPSI-ISAAC outdoor facility in Lugano, Switzerland, from April 2006 till May 2007, and the outdoor ESTER facility in Rome, from April 2008 till May 2009. Since the same module has been tested in two places using the same testing electronic unit (MPPT 3000), the device performance differences can mainly be ascribed to the different local environmental conditions. A detailed characterization of the climatic conditions in Lugano and Rome for the periods of interest have been performed and the PV module performance comparison has been carried out in terms of module efficiency, module yield (Y) and Performance Ratio (PR). No evident influence of the PV module different mounting and monitoring management has been observed on the module performance. The PR monthly trend is mainly due to the temperature influence on the module behaviour, with lower values during summer months; for the same reason, the higher temperatures experienced in Rome penalize the performance. The monthly PR appears higher for Lugano than for Rome apart from the April 07-09 case where the performance in Rome has been higher. A 3% maximum PR deviation between the two sites has been registered during the autumn months.