The contributions of additional Fe-binding sites and heme iron to the experimental spectrum of urea-influenced hemoglobin were evaluated based on theoretical analysis of X-ray absorption spectra. The theoretical Fe K-edge X-ray absorption spectra were calculated for structural models of the supposed additional Fe binding sites and heme. Linear combination fit of theoretical spectra showed that in treated hemoglobin iron ions are more likely to be in the additional Fe-binding sites, which is surrounded by the following amino acids: cysteine-93, histidine-146, and asparagine-94 (Cys93, His 146, Asp 94).