When processing graphics primitives in a graphics processing system, the render output is divided into a plurality of regions for rendering, each region comprising a respective area of the render output. It is determined for which of the plurality of regions of the render output a primitive should be rendered for. Primitive data for rendering the primitive is then stored either in a combined data structure in memory that is associated with a plurality of different regions of the render output, or is stored in a respective data structure for each region of the render output it is determined the primitive should be rendered for. Which manner the primitive data is stored is determined in dependence on a property, e.g. a coverage, of the primitive.