Differential reflectance (DR) spectroscopy has recently been reported to be effective in measuring the damage imparted to a Si surface by ion beams. Spectroscopic ellipsometry (SE) has been used extensively for this measurement. The present study compares DR and SE, ‘‘head‐to‐head,’’ from both high energy ion implanted samples (60–180 keV) and low energy (0.1–1.5 keV) ion exposures. In most cases DR and SE yield the same information, but SE has a greater analytical capability at the present time. DR is shown to be quite useful for buried layers and being simpler in terms of hardware requirements, perhaps more suitable for process monitoring.