Objectives: We retrospectively analysed patients with advanced non-small-cell lung cancer (NSCLC) harbouring high PD-L1 expression (>50%) and treated with front-line pembrolizumab, comparing outcomes of patients with an Eastern Cooperative Oncology Group (ECOG) performance status (PS) 2 to those with PS 0-1.Methods: Data were collected by 16 participating centres. All patients with NSCLC and high PD-L1, treated with first-line pembrolizumab were included. We collected medical data from patient files, pathology and laboratory reports. Patient characteristics, comorbidities, PS, and tumour characteristics were reported. Overall survival (OS), progression-free survival (PFS) and response rate (RR) were calculated.Results: 302 patients were included, 246 with PS 0-1, 56 with PS 2. RR was 72% among patients with PS 0-1 compared to 45% with PS2 (odds ratio (OR) 0.31 (95% CI: 0.17-0.57), p < .001). Median PFS was 2.6 months (95% CI: 1.9-5.1) among patients with PS2 and 11.3 months (95% CI: 8.5-14.4) among those with PS 0-1. Median OS was 7.8 months (95% CI: 2.5-10.7) in the PS2 group, not reached in the PS 0-1 group. PS 2 remained predictive of poor outcomes in multivariate analysis.Conclusion: PS 2 is a strong independent predictor of poor response and survival in NSCLC patients with high PD-L1, treated with front-line pembrolizumab. Prospective randomised trials comparing immunotherapy to chemotherapy in this population would be welcome.