Friction stir spot welding (FSSW) is a spot-like solid-state joining process suitable for welding structural components in overlap configuration. In the past few years, the use of conventional spot welding in automotive applications has become more complex due to the extensive use of lightweight alloys. FSSW has a potential to replace these conventional methods as well as to reduce manufacturing steps and lower overall costs. In FSSW the tool is not traversed and instead creates the joint by plunging into and retracting out a rotating tool of the overlapping sheets. FSSW has been performed in two different aluminium alloys - AA5754-H22 and AA6082-T6 in similar and dissimilar combination using different joining parameters (e.g. plunge rate, rotational speed and plunge depth). FSSW connections have been accomplished using same tool geometry - cylindrical 3 flute pin and flat shoulder. Mechanical behaviour has been investigated in terms of hardness, cross-tension and tensile shear. Relationships between mechanical performance and joining parameters have been established for the stir spot joints investigated. The preliminary results have shown that best mechanical behaviour has been obtained by using lower plunge rates and rotational speeds as well as higher plunge depths.