Objectives:The aims of this study were to know the frequency and clinical characteristics of insomnia, and related various factors to insomnia in patients diagnosed with thyroid disorders. Methods:For 90 patients with thyroid disorders, interviews were performed. The data were obtained from interviews from about history and assessment of insomnia and depression. Insomnia was evaluated using the Korean Version of the Insomnia Severity Index(ISI-K). According to the cutoff score of 15.5 on the ISI-K, subjects were divided into the group of thyroid patients with insomnia(n=21) and those without insomnia(n=69) at first, and then statistically analyzed. Results:1) Insomnia is found in 23.33% of patients with thyroid disorder. 2) Insomnia in patients with thyroid disorder had significantly more comorbidities of physical and psychiatric illnesses(p<0.005, respectively), more hyperthyroidism (p<0.01), higher T3(p<0.05), and longer than 60 minutes of sleep latency(p<0.001). 3) Among scores of the ISI-K, total scores(p<0.001), and scores for initial sleep(p<0.05), sleep satisfaction(p<0.005) and distress(p<0.05) were significantly higher in insomnia in patient with thyroid disorder. Conclusion:Insomnia is not rare among patients with thyroid disorder. According to the presence of insomnia, clinical characteristics including sleep quality as well as quantity seemed to be different.