Recent studies indicate that succinate dehydrogenase (SDH) genes B, C, or D are, at least partly, involved in the pathogenesis of pheochromocytoma or paraganglioma. Of these three genes, the SDHD gene mutation is most closely related with paragangliomas of the neck. Here we describe a case of an SDHD-related paraganglioma, in which we studied the molecular characteristics of an SDHD mutation to evaluate the involvement of SDHD in neck paragangliomas. Genetic testing revealed a heterozygous G106D mutation in the SDHD gene. In the tumor tissue, loss of heterozygosity was demonstrated by real time polymerase chain reaction (PCR). In the present case of SDHD mutated paragangliomas, wild type SDHD gene expression was markedly reduced possibly due to loss of heterozygosity not due to imprinting of SDHD gene in the tumors.