Resistive switching oxides are investigated at great length as promising candidates for the next generation of non-volatile memories. It is generally assumed that defects have a strong impact on the resistive switching properties of transition metal oxides. However, the correlation between different types of defect structures and the switching properties is still elusive. We deposited single-crystalline SrTiO3thin films with various cation stoichiometry by pulsed laser deposition to investigate the stoichiometry related and therefore defect dependent influence on the resistive switching properties. This letter will reveal the differences in initial states, forming steps, switching characteristics as well as retention times taking into account both point defects and extended defects. We then propose an explanation on the basis of oxygen vacancy generation and redistribution to elucidate the dependence of the resistive switching properties on the cation stoichiometry dependent defect structure.