Background: the prognosis of non-ST elevation acute coronary syndrome (NSTEACS) patients is frequently done by using thrombolysis in myocardial infarction (TIMI) and global registry of acute coronary events (GRACE) risk scores. Only few studies were done for prediction ability of the scores with coronary artery disease. Methods: this prospective cross-sectional study included 100 patients was conducted at Mabaret Misr Alqadema and Al-Azhar University Hospitals from May 2017 till September 2018. We calculated the TIMI and the GRACE risk scores for all patients on admission then patients had coronary angiography to detect the extent of the coronary artery disease (CAD). We assessed the severity of CAD by using Gensini score and vessel score. Results: the TIMI and GRACE scores have an acceptable predictive value in identifying the extent of the CAD. A TIMI score ≥3 and GRACE score ≥102 was significantly associated with 3 vessel disease and left main disease (p <0.014 for TIMI and p <0.007 for GRACE). On comparison of the two risk scores, the discriminatory accuracy of the GRACE score was nonsignificantly superior to the TIMI score in predicting 3 vessel and left main (LM) diseases but the combination of both scores has a higher accuracy (p <0.006). Conclusions: the CAD is more extensive by coronary angiography in patients with NSTEACS who had higher TIMI or GRACE risk scores, as they have a good predictive value. However, when both compared, the GRACE score has a non-statistically significant superiority with multivessel and LM disease, and combination of both scores has a higher accuracy.