A method and an apparatus for MR imaging of at least two chemical species having different MR spectra enables Dixon water/fat separation in cases in which a large field-of-view is required. The method includes the steps of: a) generating at least one echo signal by subjecting a body placed in the examination volume of a MR device to an imaging sequence of RF pulses and switched magnetic field gradients b) acquiring the at least one echo signal c) separating signal contributions of the at least two chemical species to the at least one acquired echo signal on the basis of a spectral model and prior knowledge about the spatial variation of the main magnetic field Bo in the examination volume and d) reconstructing a MR image from the signal contributions of at least one of the chemical species.
