Purpose: To compare the risk of postoperative endophthalmitis (PE) after cataract surgery at eye departments in public hospitals and private hospitals/eye clinics and to evaluate if the Danish National Patient Registry (NPR) is a reliable database to monitor the PE risk. Methods: Postoperative endophthalmitis cases were retrospectively identified via the NPR and chart review in order to confirm PE cases that had cataract surgery in the calendar period 2002-2010. Results: We identified 39 cases of PE after 107 701 registered public cataract operations; PE risk = 0.036 per 1000 operations and 27 cases of PE after 36 760 registered private operations; PE risk = 0.073 per 1000 operations. There was homogeneity in the PE risk among the eye departments in public hospitals (p = 0.6), but heterogeneity in the PE risk among the private hospitals/eye clinics (p = 0.0001). Six private hospitals/eye clinics had a statistically significantly higher PE risk compared with the eye departments in public hospitals. In all, 98% of public cataract surgery was registered in the NPR compared with 38% of private cataract surgery. The private hospitals/eye clinics with the highest PE risk after registered cataract surgery had many cases of PE where the causative cataract operation was not registered with the NPR. Conclusion: A few private hospitals/eye clinics had a statistically significantly higher PE risk than the PE risk at the eye departments in public hospitals. The lack of registration with the NPR by the private hospitals/eye clinics suggests that better monitoring of cataract surgery is needed in Denmark to reduce risk and to improve quality.