Objective: This study investigated the final hospital diagnoses and characteristics of uncooperative prehospital patients suspected of acute stroke who were unable to undergo a prehospital stroke screening test. Methods: This retrospective study was conducted from January 2015 to December 2019 to analyze the final hospital diagnoses and characteristics of uncooperative patients suspected of prehospital acute stroke. Considering the Korean emergency medical services (EMS) stroke screening policy, we also analyzed three scenario-based prehospital stroke screening performances using the final hospital diagnoses as the gold standard.Results: Of 2,836 EMS-transported adult patients who met the prehospital criteria for suspicion of acute stroke, 486 (17.1%) were uncooperative, and 570 (20.1%) had a confirmed final diagnosis of either ischemic or hemorrhagic stroke. The final diagnosis of acute stroke in the uncooperative group did not differ from that in the cooperative group (22.0% vs. 19.7%, P=0.246). The diagnostic performances in the first scenario (conservative approach) were as follows: 79.5% sensitivity (95% confidence interval [CI], 75.5%-83.1%), 90.2% specificity (95% CI, 88.8%-91.6%), and 0.849 area under the receiver operating characteristic curve (AUC) (95% CI, 0.829-0.868). No significant difference was evident in the AUC between the second (real-world approach) and third (contrahypothesis approach) scenarios (0.792 [95% CI, 0.775-0.810] vs. 0.782 [95% CI, 0.762-0.803], P>0.05). Conclusion:We provide quantitative evidence of overestimation (false positive) and underestimation (false negative) in the uncooperative group depending on the scenario-based EMS stroke screening policy for uncooperative prehospital patients suspected of acute stroke.