The clinical behaviors and treatment outcomes of thyroid carcinomas in patients with Graves' disease is a matter of controversy. This study aimed to identify the clinicopathologic features, treatment outcome, and the indicators for predicting recurrence, and to suggest the optimal extent of surgery in these patients. We retrospectively analyzed data of 58 patients who underwent surgical treatment for differentiated thyroid cancer and concurrent Graves' disease. The follow-up period ranged from 23 to 260 months (mean+/-standard deviation, 116.8+/-54.0). In our series, the mean age was 40.8+/-12.7 yr (range, 15-70), with a male-to-female ratio of 1: 6.25. The mean tumor size was 13+/-9 mm (range, 3-62). The surgical methods included 19 cases of total thyroidectomy, 38 cases of subtotal thyroidectomy, and 1 case of completion total thyroidectomy. Locoregional recurrence occurred in four patients (6.9%). The 10-yr overall survival and disease-free survival of patients were 95.8% and 91.1%, respectively. Age over 45 yr (p=0.031), tumor size over 10 mm (p=0.049), multiplicity (p=0.007), extracapsular invasion (p=0.021), and clinical cancer (p=0.035) were significantly more prevalent in patients with locoregional recurrence than in those without recurrence. We recommend that Graves' disease patients should undergo regular ultrasonography screening for early detection of thyroid carcinoma. We also suggest that the choice of extent of surgery should depend on the diagnostic timing (clinical or incidental) and factors for predicting recurrence.