This article reviews the literature on the use of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) and thallium-201, technetium-99m sestamibi and technetium-99m tetrofosmin single-photon emission tomography (SPET) for the diagnosis and staging of primary and recurrent squamous cell carcinoma of the head and neck (SCCHN). A search of the MEDLINE and CancerLit databases covering articles entered between 1989 and February 2003 was performed. In the case of FDG PET, only full-ring PET studies that included comparison with conventional morphological imaging were considered. Due to the wide variation in methodology, a straightforward meta-analysis of FDG PET literature was impossible. Instead, indicative summary receiver-operating curves of FDG PET and morphological imaging techniques were generated and a paired comparison of the sensitivities and specificities of FDG PET and morphological imaging performed. Compared with conventional morphological imaging, FDG PET proved as sensitive and specific for the detection of primary SCCHN but more sensitive and specific for the detection of cervical lymph node involvement (CLNI) and recurrence of SCCHN. Additional studies addressing the role of FDG PET in screening for distant metastases and synchronous primary tumours are mandatory. Following negative conventional evaluations, FDG PET identifies occult primary tumours in 20-50% of patients presenting with CLNI. As regards the use of 201Tl, 99mTc-sestamibi and 99mTc-tetrofosmin, more studies are required to define whether these imaging agents could form part of the current diagnostic armamentarium in SCCHN patients. It is concluded that FDG PET either is superior to or offers added value when compared with conventional morphological imaging techniques for the purpose of diagnosis and staging of primary and recurrent SCCHN.