The authors present a rare case of pyocele in the nasolacrimal duct, which was initially diagnosed as a maxillary sinus mucocele. Differential diagnosis of mucocele located in the nasolacrimal duct and of other cystic masses in paranasal sinuses is very complicated according to clinical symptoms, even with CT scan. The method of choice is surgical treatment either from an endonasal or external approach. The main goal of surgical treatment is mucocele exstirpation and permanent drainage to the nasal cavity. Pyocele is a mucopurulent cyst formed in a confined cavity lined with respiratory mucosa due to blocked natural drainage of discharge produced by seromucous glands. Conjuctival lining of lacrimal canaliculi and lacrimal sac continuously changes into ciliated epithelium with seromucous glands in nasolacrimal duct, similar to that of the respiratory epthelium in nose. The pyocele formation in our patient resulted from nasolacrimal duct blockage cranially after dacryocystectomy in childhood, and a later acquired stenosis of the remaining lacrimal duct. This led to formation of a confined cavity with respiratory mucosa lining and consequently resulted in accumulation of secretion. Pyoceles in nasolacrimal duct are very rarely diagnosed. They are often misdiagnosed for pyoceles located in the maxillary sinus. Final diagnosis is based on CT scan and histological finding of respiratory epithelium wih seromucous glands continuously changing into conjuctival lining.

        Key words: mucocele, pyocele, acquired lacrimal duct obstruction, lacrimal duct.