목적: Although most papillary thyroid carcinoma (PTC) patients show a good prognosis on initial followup, the recurrence rate for PTC after long-term follow-up is 15-45%. Multifocal PTC has higher recurrence than that of unifocal PTC. Guideline of therapeutic intervention of patients with multifocal PTC have generated considerable controversy. The purpose of the present study is to investigate the clinical features and rate of unilateral and bilateral lobe involvement in multifocal PTC, and to investigate the ratio of contralateral lobe involvement in ipsilateral multifocal PTC. 방법:The study included 645 cases of total thyroidectomy with PTC from January 2005 to December 2014. One hundred and five of the patients presented with multifocal PTC (> or = 2). The risk factors, including sex, age, tumor size, contralaterality of PTC, and lymph node metastasis were analyzed between unilateral multifocal PTC and bilateral multifocal PTC group. 결과:The mean age of the patients was 57.6 years (range, 14 - 78 years), included 28 male and 79 female. Multifocal PTC were found in unilateral lobe in 27 cases (25.7%) and bilateral lobes in 78 cases (74.3%, p = 0.037). Patients with multifocal PTC in unilateral lobe were not significantly different in sex, age, tumor size and lymph node metastasis compared with patients with bilateral multifocal PTC group. However, in multivariate Logistic an analysis, multifocality in the ipsilateral lobe on final pathology (OR = 2.44, P = 0.031) were independent predictive factors for contralateral PTC. 결론:In this study, bilateral involvement of PTC was significantly more than unilateral involvement in multifocal PTC, and ipsilateral multifocal PTC was the risk factor of contralateral PTC. But lymph node metastasis was not different in unilateral and bilateral multifocal PTC group. So,total thyroidectomy with or without neck dissection could be standard treatment not only in bilateral multifocal PTC, but also in unilateral multifocal PTC.