Method for identifying a material of an object, said material being provided with a rank i (i whole number), i being equal to one if it is at the surface and being greater than one if it is buried under i-1 layers, wherein: a°) a substantially flat surface, at least locally, of the object is irradiated with an incident beam of X photons generated by a collimated source of X photons; b°) using a collimated spectrometric detector, a first flux of X photons of a backscattered beam of X photons at an energy E 1 is measured along a given scattering angle (θ), generated after scattering of the incident beam of X photons in a first inspection volume of the material of rank i, located at a first depth in the material of rank i; c°) using the collimated spectrometric detector, a second flux of X photons of a backscattered beam of X photons at said energy E1 is measured along the same given scattering angle, generated after scattering of the incident beam of X photons in a second inspection volume of the material of rank i, located at a second depth in the material of rank i, the second depth being different from the first depth; d°) using the measurements of the two fluxes of X photons (Xi1 (E 1), Xi2), a combined attenuation coefficient u' materiau.i (E 0, E 1, ε) is calculated in which E 0 is the energy of the X photons of the incident beam of X photons and E 1 the energy of the X photons of the backscattered beam of X photons along the given scattering angle, comprising a neperian logarithm of the ratio between the two fluxes (Xi1(E 1), Xi 2 (E 1)), ε is a ratio such that ε= li'1/li1= li'2/li2, li1 respectively li2 being the distance travelled by the incident beam of X photons in the material of rank i up to the first respectively second inspection volume, li'1 respectively being the distance travelled by the backscattered beam of X photons in the material of rank i from the first respectively second inspection volume; e°) a mean μ'mean of the combined attenuation coefficient μ' materiau.i (E 0, E 1, ε) is defined over a given range of said energies E 1 of the X photons of the backscattered beam of X photons; f°) the density p of the material of rank i is estimated from the mean of the combined attenuation coefficient. a°) a substantially flat surface, at least locally, of the object is irradiated with an incident beam of X photons generated by a collimated source of X photons; b°) using a collimated spectrometric detector, a first flux of X photons of a backscattered beam of X photons at an energy E 1 is measured along a given scattering angle (θ), generated after scattering of the incident beam of X photons in a first inspection volume of the material of rank i, located at a first depth in the material of rank i; c°) using the collimated spectrometric detector, a second flux of X photons of a backscattered beam of X photons at said energy E1 is measured along the same given scattering angle, generated after scattering of the incident beam of X photons in a second inspection volume of the material of rank i, located at a second depth in the material of rank i, the second depth being different from the first depth; d°) using the measurements of the two fluxes of X photons (Xi1 (E 1), Xi2), a combined attenuation coefficient u' materiau.i (E 0, E 1, ε) is calculated in which E 0 is the energy of the X photons of the incident beam of X photons and E 1 the energy of the X photons of the backscattered beam of X photons along the given scattering angle, comprising a neperian logarithm of the ratio between the two fluxes (Xi1(E 1), Xi 2 (E 1)), ε is a ratio such that ε= li'1/li1= li'2/li2, li1 respectively li2 being the distance travelled by the incident beam of X photons in the material of rank i up to the first respectively second inspection volume, li'1 respectively being the distance travelled by the backscattered beam of X photons in the material of rank i from the first respectively second inspection volume; e°) a mean μ'mean of the combined attenuation coefficient μ' materiau.i (E 0, E 1, ε) is defined over a given range of said energies E 1 of the X photons of the backscattered beam of X photons; f°) the density p of the material of rank i is estimated from the mean of the combined attenuation coefficient.