The micro-fibril angle of specimens of Pinus radiata was measured by preparing a microsection of 1000 wood cell walls and irradiating with an X-ray beam from a synchrotron source. The (002) X-ray intensity scattered by the cellulose fibres in each wall was calculated, and the total azimuthal distribution was determined by summing the individual intensities. This is compared to the predicted intensity distributions obtained from geometrical measurements on images of real wood cell walls. The length and orientation of each of the wood cells was prepared, and based on these measurements the predicted intensity distribution was determined. It is shown that an analysis derived for square wood cells is sufficient for the accurate determination of microfibril angle, which an assumption that has not been previously verified.