Pure iron and various steel samples were yttrium implanted using the ion-implantation technique. Sample compositions and structures were investigated before and after yttrium implantation to determine the yttrium distributions and the main compounds formed after the ion implantation. Yttrium-implantation effects were characterized using analytical and structural techniques such as Rutherford backscattering spectrometry (RBS), reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD) and glancing angle X-ray diffraction (GAXRD). This paper shows that correlation between composition and structural analyses allows understanding and comparison of the surface-modification effects of implanting yttrium into pure iron and various steels before high-temperature oxidation study.