Aim: The study aims to examine the correlation between lactate, lactate clearance, CURB-65, CURB65-L, and CURB65-LC scores with mortality in pneumonia patients who were admitted to the emergency department. Material and Methods: A total of 123 patients diagnosed with pneumonia who applied to the emergency department were assessed prospectively. Lactate clearance (%): [lactate at admission -lactate at 24th hour / lactate at admission) × 100]. Statistical comparisons were made across patient groups based on lactate, lactate clearance, and CURB-65 scores. These groups included survivors and non-survivors, patients in the intensive care unit and those who were not, patients receiving mechanical ventilation and vasopressor support, and those who did not, as well as patients with a hospital stay ≤10 days and those with a hospital stay > 10 days. Results: Among patients with severe illness who did not survive and required intensive care unit admission, mechanical ventilation and vasopressor support, the lactate and CURB-65 scores were significantly higher, while the lactate clearance score was lower (p < 0.001 for all). The predictive power of CURB65-L and CURB65-LC for mortality was determined to be higher than CURB-65 and lactate clearance alone (AUC: 0.904, 0.855, 0.783, 0.834, respectively) (p<0.001 for all). Discussion: The presence of lactate, the CURB-65 score, and lactate clearance level assessed upon admission to the emergency department can serve as predictors of negative results in patients with pneumonia. In addition, the combination of CURB65-L and CURB65-LC enhances the predictive power of CURB-65 and LC individually in determining mortality.