): Gold plays a central role in the recycling of electronic scrap and especially of printed circuit boards. Established recycling processes show several significant disadvantages in this respect, such as losses during the complex mechanical pre-treatment, a very demanding and lengthy metallurgical processing and the associated enormous investment and capital commitment costs. A promising alternative approach is the selective gold recovery of printed circuit boards by means of thiosulfate leaching. While the leaching agent for gold recovery from ores has been extensively investigated, there are very few reports on the leaching of electronic scrap. To fill this research gap, in this work the influence of PCB composition and morphology was investigated using innovative conditioning techniques. Furthermore, an extensive parameter study was conducted to identify suitable process conditions, critical effects and substances and to derive the reaction mechanisms. Copper and oxygen were found to be critical components of the leaching system. Although no significant gold extraction could be achieved without these substances, an excess of them causes an enormous reagent consumption and thus prevents efficient leaching. By adjusting the solvent composition, the leaching temperature and by modification of the experimental setup, an almost complete and reproducible selective gold extraction could be achieved in less than 24 hours.