Pre-print, Working paper: We explore the competition impact on patient management in healthcare (length of stay and technical procedure's probability to be performed) by difference-indifference , exploiting time variations in the intensity of local competition caused by the French pro-competition reform (2004-2008). Models are estimated with hospital fixed effects to take into account hospital unobserved heterogeneity. We use an exhaustive dataset of in-hospital patients over 35 admitted for a heart attack. We consider the period before the reform from 2001 to 2003 and a period after the reform from 2009 to 2011. Before the reform, there were two types of reimbursement systems. Hospitals from private sector, were paid by fee-for-service. Hospitals from public sector were paid by global budget. They had no current activity's link, and a weak competition incentive. After the DRG-based payment reform, all hospitals compete with each other to attract patients. We find the reform a sizeable positive competition effect on high-technical procedure for the private sector as well as a negative competition effect on the length of stay for public hospitals. However, the overall local competition effect of the reform explained a very marginal part of the explanatory power of the model. Actually, this period is characterised by two contradictory components: a competition effect of the reform and in-patients who are more concentrated. Results suggest that if competition impacted management patient's change, it is through a global competition included in a global trend much more than a local competitive aspect of the reform.