Papillary thyroid carcinoma is the most common thyroid malignancy and frequently metastasizes to regional lymph nodes. Occasionally, metastatic lymph nodes are palpable without the evidence of primary tumour. Papillary thyroid carcinoma of lateral neck cyst is a rare condition. It may arise from thyroid primary which underwent cystic degeneration or true malignant transformation of ectopic thyroid tissue. Herein, we reported two cases with preoperative diagnosis of benign lateral neck cyst but postoperative histopathological results showed primary papillary thyroid carcinoma. Ultrasonography and computed tomography of the neck in both cases showed no significant thyroid lesion. However, the patient in Case 2 was subjected for total thyroidectomy and histopathological results showed the origin of primary tumour. In conclusion, thorough investigations including total thyroidectomy are indicated in cases of papillary thyroid carcinoma of lateral neck cyst. This practice is to ensure that this type of thyroid cancer can be detected earlier because it has a very good prognosis if treated earlier.