Background: Thoracoscore and the European Society Objective Score (ESOS.01) are two scoring systems used in thoracic surgery to estimate operative mortality risk. We aimed to evaluate if these are valid tools for use in the UK population. Methods: A multi-center, prospective study was carried out on patients undergoing lung resection at six UK centers. Data were submitted electronically using our online data collection tool. Data were analyzed to determine the factors affecting mortality. A receiver operating characteristic analysis determined the ability of the thoracoscore and ESOS.01 to predict in-hospital mortality. Results: Data were complete for 2,245 patients. The observed in-hospital mortality was 31 patients (1.38%). Mean thoracoscore was 2.66 (SD ± 3.21). Gender (P = 0.004, hazard ratio 4.786) and co-morbidity score (P = 0.005, hazard ratio 3.289) were identified as risk factors for mortality. A sub-analysis was performed using data from 1,912 patients with complete data for ESOS.01. In this group, mean thoracoscore was 2.55 (SD ± 2.94), mean ESOS.01 was 2.11(SD ± 1.41), and these were statistically significantly different (P < 0.0001). The observed in-hospital mortality was 28 patients (1.46%). The c-index for thoracoscore was 0.705, and for ESOS.01 was 0.739. Conclusions: Both thoracoscore and ESOS.01 overestimated mortality in the UK population. There is a continued need to develop an appropriate risk prediction system for the UK.