On the basis of photon–matter interactions landscape, γ-rays shielding effectiveness of light density polyethylene (LDPE) composites reinforced with different percentages of micro- and nano-PbO, WO۳, ZnO, and TiO۲ particles was studied. Using voxelization in MCNPX code, metal oxide particles with sizes of ۱۰۰ nm, ۱ µm, and ۱۰۰ µm and proportions of ۱۰, ۲۵, and ۵۰ wt% were designed inside a LDPE matrix. Narrow beam geometry was simulated to calculate the mass attenuation coefficient of structures against photons in a wide energy region of ۰.۰۱۵– ۱۵ MeV. Although the significant role of filler size and proportion in attenuating X- and γ-rays was confirmed, the results indicated that application of PbO and WO۳ particles in reinforcing polymeric matrix provides greater photon attenuation compared to those doped with ZnO and TiO۲ particles. Besides, it was found that attenuation performance of the LDPE/metal oxide composites is superior in the low energy range.