Background: Ventilation-perfusion (VQ) scintigraphy and lung function testing are often used to assess allograft function after single lung transplantation (SLTX). However, it is unknown whether allograft defects on VQ scintigraphy presage all-cause mortality after SLTX. Objective: To investigate whether allograft defects on VQ scintigraphy portend poorer lung function and increased mortality after SLTX. Methods: We retrospectively identified 45 consecutive patients in which a VQ scintigraphy was performed as part of the routine workup 12 weeks after SLTX. VQ scintigraphies were scored for matched and mismatched perfusion defects in the allograft. Lung function testing was performed according to established guidelines six months after SLTX. Time to all-cause mortality was the endpoint. Results: 19 (42%) patients had matched VQ defects. After a median follow-up of 4.1 (IQR 1.5–7.9) years since SLTX, 35 (78%) had died. Those with matched defects in the allograft had lower diffusing capacity (mean 42 [SD 14] versus mean 54 [SD 18] % of predicted, p <.05) and increased mortality (univariable HR 2.06, 95% CI: 1.05–4.06, p =.04). However, in multivariate analysis, only lower post-transplantation diffusing capacity remained associated with mortality (HR 1.08, 95% CI: 1.02–1.30 per % lower diffusing capacity of predicted, p =.003). Conclusion: In SLTX patients, a lower diffusing capacity appeared to explain the increased mortality among those with matched VQ defects in the allograft.