Although quality of life (QoL) has become an important aspect of cancer rehabilitation, psychometric studies on thyroid cancer patients are rare. We performed a case-controlled study on QoL in patients with differentiated thyroid carcinoma (DTC). QoL was evaluated in 61 patients with a history of DTC diagnosed from < 1 to 23 yr earlier. An undetectable thyroglobulin (Tg) level after recombinant human TSH (rhTSH) testing was considered the best predictor of cure. QoL was evaluated by means of a general psychiatric interview, the self-rating Kellner Symptoms Questionnaire (KSQ) and the Hamilton Depression Scale (HDS). QoL was also evaluated in a control group of subjects on L-T4 therapy with a non-toxic multinodular goiter diagnosed from < 1 to 25 yr earlier. DTC and control subjects were similar in age, male-female distribution and concomitant psychiatric therapies. Per-week dosage of L-T4 was higher in DTC patients than in controls (p < 0.01). In neither group of subjects was there any correlation between current TSH levels or interval from diagnosis and KSQ or HDS scores. Only in DTC patients was there a positive correlation between age and KSQ (p < 0.05) or HDS (p < 0.01) scores. There was a significant difference in overall KSQ scores between DTC (33.4 +/- 2.1) and control (24.5 +/- 1.9; p < 0.01) subjects. The subscales of KSQ showed a significant inter-group difference. HDS scores were higher in DTC subjects (35.8 +/- 1.0) than in controls (30.0 +/- 1.1; p < 0.01). HDS score was significantly (p = 0.02) higher in female than in male DTC patients. In patients with papillary carcinoma there was a positive correlation between the MACIS (metastases, age, completeness, invasiveness, size) score and KSQ (p = 0.01) or HDS (p < 0.01) scores. After rhTSH testing, detectable Tg levels were found in 13% of DTC patients. In Tg-positive patients, KSQ and HDS scores were not different from those of Tg-negative patients. After an 8-14 month period, a significant decrease in the KSQ scale somatization (p = 0.02) was found in a sub-set of 31 DTC patients. In conclusion, even in the age of rhTSH testing, DTC patients suffer an impairment of their QoL, as noted when short-term L-T4 withdrawal was the gold standard. Longitudinal evaluation seems to indicate a slight improvement in QoL when safe rhTSH testing is extensively used in the management of the disease.