According to well documented histories a group of experts-endocrinologists determined the presence of one or another disease in 109 patients with different thyroid pathology. Two examinations were performed according to the clinical findings and on the basis of the same indices, added by results of the radioiodine test. Diagnostic informativity of different indices of the radioiodine test was evaluated according to the correlation (by means of calculation of the correlations) between the radiological parameter and the disease probability. It was concluded that the parameters of the routine research methods (131I absorption within 2, 4, 24 and 48 hours) are more informative than the values of more complicated variants of the radioiodine test. Informativity of the whole radiological and non-radiological findings was estimated, using a diagnostic coefficient method. It was shown that the role of radiological indices in making a correct diagnosis averages 17% and in cases of hypothyrosis and toxic forms of goiter this value increases up to 30%.