Using a French exhaustive dataset, this paper studies the determinants of regional disparities in mortality for patients admitted to hospitals for a heart attack. These disparities are large, with an 80% difference in the propensity to die within 15 days between extreme regions. They may reflect spatial differences in patient characteristics, treatments, hospital characteristics, and local healthcare market structure. To distinguish between these factors, we estimate a flexible duration model. The estimated model is aggregated at the regional level and a spatial variance analysis is conducted. We find that spatial differences in the use of innovative treatments play a major role whereas the local composition of hospitals by ownership does not have any noticeable effect. Moreover, the higher the local concentration of patients in a few large hospitals rather than many small ones, the lower the mortality. Regional unobserved effects account for around 20% of spatial disparities.