The strength and paint bake response of heat treatable aluminium auto body sheet material are important material properties. These are not only influenced by the alloy composition but also by the processing cycle. And after producing material in T4 or T4P condition the effect of natural ageing needs to be considered. The effect of alloy composition on the paint bake response is widely investigated. Most of the results presented were focused on non-preaged material (in the so-called T4 condition). For those cases copper is in general accepted to enhance the precipitation hardening kinetics, improving the strength development of the alloy during paint baking. However, there is a clear market demand to develop preaged material to improve the paint bake response. Therefore the influence of copper addition (in combination with preageing) on the final paint bake response needs to be evaluated. In this study the influence of copper on the paint bake response of preaged AA6xxx alloy has been examined, varying the Cu concentration between 0 and 0.75 wt%. The T4, T4P and T6 strength has been evaluated as function of the copper concentration. Four different alloys are cast on laboratory scale, homogenised, hot rolled, cold rolled and solution heat treated. The samples are preaged to T4P condition and tested in the T4P and T6 conditions. It was found that with increasing copper concentration the paint bake response showed a tendency to decrease.