The KUL-UCL-UG consortium has been contributing since 2003 (thanks to the support of the Foundation against Cancer) to validate the use of molecular imaging in Target Volume (TV) delineation for the treatment of head and neck (H1N), and rectal cancers. In line with the previous researchprojects, the general aim of the study proposal is: 1) to validate the dose-painting approach to escalate radiation dose on TV(s) delineated onPET images using tracers of metabolism, hypoxia and proliferation. In H&N tumores, a randomized phase II will be launched with loco-regional control as the primary endpoint; in lung tumors (NSCLC), a phase II study will be launched; 2) to validate the use of molecular imaging with PET and DW-MRI for response prediction early on during the course of concomitant chemo-radiotherapy. Response will be assessed on the surgical specimen for rectal cancer (pre-op chemo-radiation), or on imaging during the follow-up for H&N cancer and NSCLC; 2) to validate the use of molecular imaging with PET and DW-MRI for response prediction early on during the course of concomitant chemo-radiotherapy. Response will be assessed on the surgical specimen for rectal cancer (pre-op chemo-radiation), or on imaging during the follow-up for H&N cancer and NSCLC; 3) to test the convergence of molecular imaging and molecular profiling for prediction of tumor response in patients with H&N, rectal and NSCL cancers.