Interregional patient mobility in a decentralized healthcare system. Regional Studies. Interregional patient mobility, measured as origin–destination patient flows between any two regions, is analysed within a dynamic spatial panel data framework using 2001–10 data on Italian hospital discharges. The aim is to assess the effects of the main determinants of patient flows, distinguishing between the impacts of regional health policies and those exerted by exogenous factors (geography, size, neighbouring regions, national policies). Empirical results indicate that the main drivers of mobility are regional income, hospital capacity, organizational structure, performance and technology. Moreover, neighbouring regions’ supply factors, specialization and performance largely affect mobility by generating significant local externalities.