Radionuclide thyroid scanning of patients with Hashimoto's thyroiditis (HT) may mimic other thyroid disorders including cold nodules, multinodular goiter and rarely hot nodules. The association of single hot nodules in such patients in the face of primary hypothyroidism has not been previously reported. We describe 6 female patients with HT who presented either with symptoms of overt thyroid failure or a sensation of lump in the neck (and later found to have mild thyroid failure) who had single firm thyroid nodules. These nodules were hot by both 99mTc pertechnetate and radioiodine thyroid scans. In three of 4 patients followed up for longer than 6 months on adequate thyroid replacement therapy the nodules regressed by up to 60%. Given "Best practice" recommendations patients with thyroid failure and single thyroid nodules would not be submitted to radionuclide scanning and this presentation of HT would have gone undetected.