This paper proposes to investigate the effect of spillovers on location decision of firms. We develop an analysis merging the geographer toolbox with the standard econometric techniques. For a chosen sample of sectors, through the spatial data analysis, we test the existence of positive spatial autocorrelation for R&D investments that lead R&D expenditure to cluster. Moreover, we succeed in detecting in how far the local environment may influence the firm decisions in R&D investments. Data confirm that the proximity to other firms investing in R&D may produce positive externalities. Finally, the diversity vs. specialization debate is tackled.