A variety of nanocomposites were synthesised by bulk polymerisation of methyl methacrylate (MMA), and also by extrusion of poly(methyl methacrylate) (PMMA). These were characterised by wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). We applied image analysis to the TEM images of these PMMA-clay nanocomposites to quantify their structures; an analysis was made of the resulting parameters to determine which were most useful for quantifying the microscale and nanoscale structures. Frequently, these quantitative results differed from those expected on the basis of WAXD, demonstrating the limitations of using diffraction data as the sole measure of nanocomposite structure. By combining the quantitative parameters from TEM with the WAXD data, we have explored the effects of processing conditions and organoclay properties on final nanocomposite structure. Factors examined included the effect of the reactivity of the surface modifiers, platelet size, the incorporation of excess modifier within the organoclay, and bulk polymerisation versus extrusion.