We presented two adult cases of cystic hygroma colli (CHC), one with atypical location. The first patient was a 23-year-old male with CHC located in the posterior cervical triangle, its common location in the neck. The latter was a 22-year-old male whose lesion occupied the submandibular region and extended to the skull base. The diagnosis was made by computed tomography, magnetic resonance imaging, and fine-needle aspiration biopsy, and confirmed by postoperative histopathologic examination. The lesions were surgically removed in both patients, and no recurrence was encountered during postoperative 12 and 14 months, respectively.