Disruptions are a critical issue for large scale tokamak due to a risk of damage to the plasma facing components. Massive Gas Injection (MGI) is considered as a 'last resort' method for disruption mitigation. A MGI system based on the disruption mitigation valve has been brought into operation at JET. Injections of neon in the range of 0.16-0.9kPa·m3, argon (0.12-0.86kPa·m3) and its mixtures with deuterium (0.24-1.28kPa·m3) show distinct effects on the machine condition during and after MGI-induced disruptions. This contribution focuses, using mass and VUV spectroscopy, on the impact of MGI on the wall conditions.