The complications of concurrent chemoradiotherapy for nasopharyngeal carcinoma include dryness of mouth, sensorineural hearing loss, dental caries, trismus, pituitary dysfunction, myelitis, paralysis of cranial nerves IX–XII, massive neck fibrosis and pharyngeal wall necrosis. Tornwaldt's cyst formation after concurrent chemoradiotherapy for nasopharyngeal carcinoma has not been reported previously in the world literature. Tornwaldt's cyst, a persistent pharyngeal bursa, is found in about 3 per cent of the adult population, although the majority of these are asymptomatic. We describe the previously unreported complication of Tornwaldt's cyst formation after concurrent chemoradiotherapy for nasopharyngeal carcinoma.