The objective was to assess the patient-relevant benefit of PET or PET/CT in patients with thyroid cancer based on a literature review and meta-analysis. To be included, studies had to prospectively investigate patients with thyroid cancer in a clinical setting of staging, restaging or diagnosing tumour recurrence. Out of 3506 potentially relevant articles, 29 studies were included. Twenty-eight studies dealt with the diagnostic accuracy of PET or PET/CT, and one study evaluated the prognostic value of PET/CT. The authors showed that a positive result of PET/CT in restaging patients with differentiated thyroid cancer yielded a significant decrease in overall survival. In patients with suspected recurrence of differentiated thyroid cancer, meta-analysis showed higher sensitivity of PET and PET/CT compared with conventional imaging and comparable results for specificity. Due to low numbers of studies and patients, meta-analyses on medullary carcinoma did not produce meaningful results.