In out-of hospital settings (OHS), various Trauma Scores (TS) are useful as significant trauma outcome predictors. This study was to retrospectively calculate the RTS (Revised Trauma Score), MGAP (Mechanism of Injury, GAP-Glasgow Coma Score, Age, Arterial Pressure) and GAP values and then compare them as mortality predictors in OHS. A cross-sectional study was conducted on 286 trauma patients (TP) in OHS treated from 1st to 31st October 2020 and transported to the Clinical Center of Serbia (CCS). The data analysed came from medical reports filled out by the IEM Belgrade doctors and the discharge papers from the CCS. Clinical and demographic variables for all the subjects, as well as their GAP, MGAP, and RTS scores, were examined. Their AUC values were compared. While analysing the ability of the GAP, MGAP and RTS scores to predict in-hospital mortality, we found comparable values at 0.890 (GAP), 0.869 (MGAP) and 0.871 (RTS) by using the AUROC curve with high statistical significance (p< 0.001). MGAP has the highest sensitivity, and GAP has the highest specificity. No significant difference in the ability to predict mortality between these three scores. Clinical parameters and calculated TS for all TP classified according to whether the subjects survived (n=230; 80.5%) or died (n=46; 19.5%) after four weeks of treatment in the CCS were significantly statistically different in these two groups. GAP, MGAP and RTS scores are significant predictors of poor outcomes and mortality in TP. It was established that there is no difference in their predictive value.