As tin based electrodes are of significant interest in the development of improved lithium-ion batteries it is important to understand the associated electrochemical reactions. In this work it is shown that the electrochemical behavior of SnO 2 coated tin electrodes can be described based on the SnO 2 and SnO conversion reactions, the lithium tin alloy formation and the oxidation of tin generating SnF 2. The CV, XPS and SEM data, obtained for electrodeposited tin crystals on gold substrates, demonstrates that the capacity loss often observed for SnO 2 is caused by the reformed SnO 2 layer serving as a passivating layer protecting the remaining tin. Capacities corresponding up to about 80 % of the initial SnO 2 capacity could, however, be obtained by cycling to 3.5V vs. Li +/Li. It is also shown that the oxidation of the lithium tin alloy is hindered by the rate of the diffusion of lithium through a layer of tin with increasing thickness and that the irreversible oxidation of tin to SnF 2 at potentials larger than 2.8V vs. Li +/Li is due to the fact that SnF 2 is formed below the SnO 2 layer. This improved electrochemical understanding of the SnO 2/Sn system should be valuable in the development of tin based electrodes for lithium-ion batteries.