X-ray diffraction images from two-dimensional position-sensitive detectors can be characterized as thick or thin, depending on whether the rotation-angle increment per image is greater than or less than the crystal mosaicity, respectively. The expectations and consequences of the processing of thick and thin images in terms of spatial overlap, saturated pixels, X-ray background and I/σ(I) are discussed. The d*TREK software suite for processing diffraction images is briefly introduced, and results from d*TREK are compared with those from another popular package.