We report a false positive case of I-131 scan due to a sialolithiasis in right submandibular gland. I-131 images showed not only remnant thyroid tissues and functional metastases in the anterior neck but also a hot uptake near right submandibular gland. We confirmed the sialolithiasis by radiologic studies. Sialolithiasis should be regarded as a false positive cause when I-131 scan shows a hot spot near salivary bed.