After radiotherapy with or without chemotherapy differentiation between residual and recurrent head and neck cancer and (chemo)radiation sequelae is often difficult. Currently, most physicians aggressively pursue potential recurrences, leading to a high rate of futile invasive diagnostic, e.g. examinations under general anaesthesia with taking of biopsies, and surgical procedures, e.g. planned neck dissections, and a waste of health care resources. Therefore, diagnostic techniques which reliably select patients who should undergo these procedures are warranted. Conventional imaging techniques are not reliable enough for this purpose. Potential imaging techniques to detect residual and recurrent locoregional disease after chemoradiation are (serial) CT or MRI and FDG-PET, eventually in combination with specific response criteria or scoring systems. Diffusion MRI and PET/CT may further improve these techniques. FDG-PET may help to select patients clinically suspected of recurrent laryngeal carcinoma after radiotherapy for direct laryngoscopy under general anaesthesia. It is not yet clear whether FDG-PET can reliable avoid futile routine evaluation by examination under general anaesthesia in oral and oropharyngeal cancer and planned neck dissection when a residual mass persists in the neck after (chemo)radiation. The most reliable scoring criteria and the optimal time interval between completion of radiation and FDG-PET still has to be assessed.