The present invention relates to a method and apparatus for X-ray phase contrast imaging. The method comprises the following steps: from the measured phase gradient and overall attenuation information, an electron density is computed; the contribution pc of the Compton scattering to the overall attenuation is estimated from the electron density; the contribution pp of the photo-electric absorption to the overall attenuation is estimated from the overall attenuation and the contribution pc; the values pc and pp are used to reconstruct a Compton image and a photo-electric image; by linear combination of these two images, a monochromatic image at a desired energy is obtained.