Pleomorphic adenoma is the most common benign salivary gland tumor. However, other localisations, such as intranasal and especially in ethmoidal cells, are exceptionally rare. We present a 55 years old female patient with right-sided watery discharge accompanied with gradually increasing nasal obstruction. Radiology revealed round solitary mass, arising from the posterior ethmoidal cells on the right side. Histological examination diagnosed pleomorphic adenoma. Analysis of the watery discharge revealed cerebrospinal liquid. Treatment consisted of endoscopic excision of the tumor and closure of the liquorrhea. Patient is on follow-up for 12 months. Recurrences of disease were not revealed. Presented case report is the first know report in the English literature when main symptom was nasal liquorrhea. This case presents high clinical interest as it shows how long and inappropriate diagnosis and treatment can lead to serious consequences.