We investigate whether top managers affect the performance of large public sector organizations. As our case study we examine CEOs of English public hospitals, which are large, complex organizations with multi-million turnover. We study the impact of individual CEOs on a wide set of measures of hospital performance, intermediate operational outcomes and inputs. We adopt two econometric approaches: a parametric approach that exploits the movement of CEOs across different hospitals and a non-parametric difference-in-difference matching estimator. Overall, we find little evidence that individual CEOs have an impact on a large set of measures of hospital performance. This result is not due to the allocation of good performers to poorly performing hospitals.