We analyzed Radioisotope scan findings of 46 patients of thyroiditis which were proven pathoiogically at K.C.FI. The results were as follows 1) 45 patient.s were female, one was male and average age of patients was 37 years old. 2) The lesion site was predominant in both lobe (67%) Hashimotos thyroiditis showed enlarged thyroid (85%) with cold nodule (20%), diffuse decreased activity (10%), while subacute thyroiditis was presented absent activity (53%), poor visualization (20%) or cold nodule (7%). 4) Radioisotope scan was valuable in evaluationg function of thyroid gland and detection of lesion but there was a limit of pathological nature.