Objective: To compare the efficacy between diffusion-weighted magnetic resonance imaging (DW-MRI) and positron emission tomography/computed tomography (PET/CT) in detecting the local recurrence of head and neck squamous cell carcinoma (HNSCC) following treatment in the same patient group. Methods: Twenty-three patients who had biopsy-proven HNSCC were enrolled. All patients were treated with radiotherapy and followed up with MRI and PET/CT. The median delay times between radiotherapy and MRI and between MRI and FDG PET/CT were 71 days (range: 43-98 days) and 75 days (range: 44-103 days), respectively. Diffusion-weighted single-shot echo planar imaging was performed before contrast injection at b values of 0 and 1000 s/mm2. PET/CT images were acquired after the administration of 3.7 MBq/kg of fluorine-18-fluorodeoxyglucose, and the images were acquired 1 h later.Results: The apparent diffusion coefficient (ADC)mean values of the recurrence group were significantly lower than those of the post-treatment changes group (0.773 vs. 1.588×10-3 mm2/s, respectively; p<0.001). The standardized uptake value (SUV)max values of the recurrence group were significantly higher than those of the post-treatment changes group (15.642 vs. 4.508, respectively; p<0.001). There was no significant correlation between ADC(r=0.341; p=0.278), whereas there was a negative correlation between ADCmeanand SUVmax values of the post-treatment changes (r=-0.691; p=0.019).mean and SUV values of recurrence max Conclusion: PET/CT and DW-MRI are effective methods for distinguishing recurrence from post-treatment changes. Follow-up should begin with DW-MRI, and in patients with a suspicion of recurrence, PET-CT should be added to the follow-up protocol.