In the present study we use x-ray diffraction methods to characterize the surface of Si wafers irradiated with nitrogen by Plasma Immersion Ion Implantation. This is a non-line-of-sight ion implantation method, which allows three-dimensional treatment of materials including semiconductors, metals and dielectrics. The atomic concentration profiles in the implanted Si wafers were measured by Auger electron spectroscopy. The (004) Si rocking curve ( omega-scan) was measured in a high resolution x-ray diffractometer equipped with a Ge (220) four-crystal monochromator before and after implantation. A distortion of the Si (004)-rocking curve was clearly observed for the as-implanted sample. This rocking curve was successfully simulated by dynamical theory of x-ray diffraction, assuming a Gaussian strain profile through the implanted region. The analysis made by x-ray difraction and Auger electron spectroscopy revealed successful implantation of ions with ac- cumulated nitrogen dose of 1.5 x <FONT FACE=Symbol>10(17) </FONT>cm-3 .The Si wafers can be used as high sensitivity monitors in the Plasma Immersion Ion Implantation process, especially at the low dose range.