Determining Fractional Flow Reserve (FFR) often relies on invasive methods, which have practical and cost limitations. This study, conducted on a sample of 15 patients with varying degrees of stenosis in the blood vessel walls, explores computer simulations as a non-invasive alternative. FFR values were measured for the left and right coronary arteries during individual diagnostic cardiac catheterizations. These measured values were compared with those obtained through numerical simulations using specialized software tools and packages for geometrical modeling and blood flow simulation. The study's results are visually presented and analyzed, showing a high degree of agreement between the measured and simulated values. An additional evaluation was performed by analyzing absolute and relative error values for both coronary arteries. The calculated absolute error values ranged from 0.01 to 0.04 for the right coronary arteries and from 0.01 to 0.05 for the left coronary arteries, indicating a strong alignment between the simulated and measured values. Furthermore, relative errors were calculated to further validate the study's findings. The relative error values ranged from 1.04% to 4.71% for the right coronary arteries and from 1.04% to 5.62% for the left coronary arteries.