Several systems enabling the evaluation of prognosis for patients with differentiated thyroid cancers include, together with some other clinical variables, such ones as patient’s tumor size and age. Associations between these prognostic factors are not yet completely understood; that is why the aim of this investigation was to study the frequency of thyroid papillary carcinoma spreading with different tumor aggressive characteristics depending on patient sex and age as well as on primary neoplasm size. All these three factors are significant for the disease prognosis, their impact being, however, not the same. The results suggest the tumor size as well as patient age and sex to be also essential and to impact on the spreading of tumor characters determining their aggressiveness. The effect of the tumor size differs in patients of different sex and age.