Abstract: A method for marking titanium dioxide pigment particles, as well as a method for identifying and verifying products via the marked titanium dioxide pigment particles contained in these products. The marker substance(s) is/are added during titanium dioxide production, preferably during surface treatment, drying or steam-milling. Particularly suitable as marker substances are the lanthanides, yttrium, zinc, molybdenum, tungsten, germanium, tin and scandium. The method is used to verify authentic product, to identify product forgeries (product piracy), to track distribution channels, or to identify the pigment used in order to counter unjustified complaints. It can be used in the product segments: fibres for textiles, papers for documents, pharmaceuticals, and also for plastics and coatings.