Abstract The surface geometries of two series of organic pigments, β-copper phthalocyanines and calcium 4B toners, have been analysed by a fractal approach, in which surfaces are characterised by a dimensional scale, D. For surfaces of progressively higher irregularity, the value of D rises from 2 (perfectly two-dimensional) towards 3 (perfectly three-dimensional). In view of the anisotropy of both types of pigment crystal, values of D were determined in terms of two crystal dimensions. The values, 2.26 and 2.29, obtained with respect to breadth and length of the β-copper phthalocyanine crystals suggest that their surfaces are by no means smooth. Fractal analysis of the calcium 4B toners suggests that the side faces of their crystals are smoother (D = 2.06), but information about the main faces is less clear. The nature of the aggregate structures also has a bearing on fractal analysis and examples are discussed for both series of pigments.