<p>Polymethyl methacrylate (PMMA, C₅H₈O₂) is widely used as a human breast tissue equivalent in medical X-ray technology. PMMA is preferred for reference and dosimetry measurements due to the resemblance in breast tissue’s attenuation and scattering characteristics. This study aims to correctly obtain the theoretical linear attenuation coefficients and the differential linear coherent scattering profile of PMMA. The calculations were produced by numerical integration based on the diffraction properties and small-angle scattering. The results were obtained with a different approach method and compared with experimental and theoretical counterparts. The close similarities of PMMA to attenuation and scattering properties of carcinoma and fibroglandular breast tissues were shown in the mammography energy range. When the theoretical linear attenuation coefficients were compared with the XCOM data widely used in the literature, it was seen that the present results were 7.02–12.10% closer to the experimental findings than the XCOM data in the energy range of 20–30&#xa0;keV. The attenuation coefficients are of great interest to medical research. We strongly believe that our results will give valuable information for breast tissue characterization and modeling in MC code.</p>