The chemical properties and electrical transport properties of SnOx doped In2O3 (ITO) and their differences between single crystals prepared by chemical vapour transport, fine powders (150...200 nm particle size) and weakly sintered ceramics (1100 degrees C, 24h, about 50% of theoretical density) were reported. In single crystals the minimal resistivity is found at the solubility limit of SnOx (8.2 mol%), whereas in ceramics and fine powders a minimum occurs at lower concentrations which is connected with a strong surface segregation of SnOx.