The aim of the study was to define the cost-effectiveness of whole-body 18 F-FDG PET, as compared with chest CT, in screening for distant metastases in patients with head and neck squamous cell carcinoma (HNSCC). Methods: In a multicenter prospective study, 145 consecutive patients with high risk factors for distant metastases and scheduled for extensive treatment underwent chest CT and whole-body 18 F-FDG PET for screening of distant metastases. The cost data of 80 patients in whom distant metastases developed or who had a follow-up of at least 12 mo were analyzed. Cost-effectiveness analysis, including sensitivity analysis, was performed to compare the results of 18 F-FDG PET, CT, and a combination of CT and 18 F-FDG PET (CT 1 18 F-FDG PET). Results: Pretreatment screening identified distant metastases in 21% of patients. 18 F-FDG PET had a higher sensitivity (53% vs. 37%) and positive predictive value (80% vs. 75%) than did CT. CT 1 18 F-FDG PET had the highest sensitivity (63%). The average costs in the CT, 18 F-FDG PET, and CT 1 18 F-FDG PET groups amounted to e38,558 ($57,705), e38,355 ($57,402), and e37,954 ($56,801), respectively, in the first year after screening. CT 1 18 F-FDG PET resulted in savings between e203 ($303) and e604 ($903). Sensitivity analysis showed that the dominance of CT 1 18 F-FDG PET was robust. Conclusion: In HNSCC patients with risk factors, pretreatment screening for distant metastases by chest CT is improved by 18 F-FDG PET. The combination of 18 F-FDG PET with CT is the most effective, without leading to additional costs.