OBJECTIVE: The prevalence of Thyroid-Cancer (TC) has increased worldwide and an association with metabolic and cardio-vascular disorders has been reported. Moreover, an increasing percentage of patients are currently diagnosed incidentally through non-thyroid related imaging for other clinical conditions. Our aim was to assess the prevalence of Thyroid-Related (TD) versus Incidental (ID) pre-surgery reasons leading to TC diagnosis and to compare the two groups in terms of clinical characteristics, size and severity of TC at presentation and rate of non-thyroid cancers and cardiovascular/metabolic comorbidities. DESIGN: we performed a retrospective cohort study in three high-volume hospital-based centers for thyroid diseases (Pavia, Latina and Messina) in Italy. PATIENTS: Consecutive patients with TC Measurements: data on pre-surgery reasons leading to TC diagnosis, age, sex, BMI, presence of cardio-metabolic comorbidities and non-thyroid cancer. RESULTS: among the 327 enrolled subjects the diagnosis of TC was prompted by thyroid-related reasons in 262 (80.1%, TD group) and incidental in 65 (19.9%, ID group). The ID group patients were more frequently males, significantly older and with a higher BMI than the TD group ones, they had a higher rate of non-thyroidal cancers and cardiovascular/metabolic comorbidities. No significant differences could be observed in terms of TC histotype, cancer size, extra-thyroidal extension, lymph-node metastases, AJCC Staging or ATA Risk stratification. CONCLUSIONS: biological features of TC are similar in the TD and ID groups, but patients in the two groups display significant differences regarding their clinical features.