In this paper new kinetic results obtained in the two step tin anchoring process are summarized. In this tin anchoring process the key step is the controlled surface reaction (CSR) between tin tetraalkyl and hydrogen adsorbed over platinum. In this study the focus was laid on the influence of the duration of tin anchoring on the type of surface organometallic species formed. The results of temperature programmed decomposition (TPD) of surface organometallic species in a hydrogen atmosphere indicated that at the beginning of tin anchoring, i.e. at low tin coverage, one of the main surface species is Sn(C 2 H 5 ) 4 strongly adsorbed into platinum. As the surface reaction proceeded the amount of tin anchored increased and the strongly adsorbed form of Sn(C 2 H 5 ) 4 was transformed into surface species with general formula of -Sn(C 2 H 5 ) (4-x) , and -{Sn(C 2 H 5 ) (4-x) [Sn(C 2 H 5 ) 4 ]}. This behavior has been well-demonstrated on different supported platinum catalysts at relatively low [Sn] o /Pt s ratios ([Sn] o /Pt s < 2). Under this condition monolayer tin coverage can be achieved, i.e. the ratio of Sn anch /Pt s in the formed alloy type supported Sn-Pt catalysts is around 0.4-0.5.