 Metabolic imaging of tumors using PET and the glucose analog FDG has proven effective in head and neck SCC, especially after treatment to differentiate disease progression from radiation-induced inflammation.1 Several studies have shown that the metabolic response could predict the presence or absence of residual tumor cells in the primary tumor as well as the probability of relapse .2-4 Conflicting results have been reported on the use of PET to predict the pathological nodal status after chemoradiation, with negative predictive values ranging from 14 to 100 .5,6 Discrepancies observed might be due to the fact that PET was performed at variable time points after the end of radiotherapy. Ideally, PET should be performed as late as possible so that tumor regrowth can begin and become detectable, increasing the sensitivity of the procedure. 