Introduction: Current stroke guidelines do not give uniform recommendations regarding the use of CT perfusion (CTP) for the selection of patients presenting within six hours after symptom onset for endovascular treatment (EVT). Model-based analyses can be used to estimate the potential long-term costs and health effects of CTP for patient selection. Methods: In this nationwide retrospective cohort study with model-based health economic evaluation, 703 large vessel occlusion acute ischemic stroke patients with CTP imaging and EVT within six hours after symptom were included (Inclusion: January 2018 - March 2022; trialsearch.who.int:NL7974). CTP-based EVT patient selection using varying ischemic core volumes (ICV) and core-penumbra mismatch ratios (MMR) was compared with providing EVT to all patients. Net monetary benefit (NMB) at a willingness to pay of 80,000 Euro per quality-adjusted life year, the incremental cost-effectiveness ratio (ICER), the difference in costs (dCosts), and quality-adjusted life years (dQALY) per 1000 patients were the outcome measures. Results: The cohort of patients with CTP and EVT used for simulations consisted of 391/703 males with a median age of 72 (IQR:62;81). Considering the most optimal ICV (>110mL) and MMR (<1.4) thresholds, CTP-based selection for EVT resulted in a loss of health (dQALYs: ICV-median:-3.3[IQR:-5.9;-1.1], MMR median:0.0 [IQR:-1.3;0.0]), limited additional costs or cost savings (dCosts: ICV-median:-348,966[IQR:-712,406;-51,158], MMR-median:266,336[IQR:229,403;380,095]), and an ICER and NMB with a wide IQR (ICER ICV-median:71,346[IQR:-16,517;181,241], MMR-median:312,955[IQR:-141,379;infinite]) (NMB ICV-median:102,227[IQR:-282,942;431,923], MMR-median:-278,850[IQR:-457,097:-229,403]). Conclusion: In EVT-eligible patients presenting within six hours after symptom onset, excluding patients based on CTP parameters was not cost-effective and could potentially harm patients.