Parathyroid cysts are unusual and do not have specific clinical manifestations or ultrasonographic findings. Therefore, they are usually confused with thyroid nodules. We report a 43 years old male, with normal thyroid function and normal calcium serum levels, that presented a nodule in the lower right third of the neck. Ultrasonography and CAT scan showed a well delimited 6 x 4.5 cm ovoid cyst that compressed and displaced the trachea and esophagus. A fine needle aspiration was done on three occasions, extracting 18, 40 and 60 ml of liquid. As the cyst recurred and symptoms intensified, the patient was operated removing the cyst and the right thyroid lobe. Pathological study disclosed a parathyroid cyst (Rev Méd Chile 2003; 131: 432-5).