Purpose : We performed this study to evaluate the most common site of the nasolacrimal systemic obstructionand causes of the nasolacrimal stent insertion failure and reobstruction following the insertion of the stent.Material and Methods : Nasolacrimal stent insertion was attempted in 26 cases(24 patients) of 30 cases (25patients) with complete obstruction of the nasolacrimal system at the dacryocystography. We retrospectivelyassessed the obstruction site of nasolacrimal system, and evaluated the rate and causes of stent insertion failureand reobstruction following insertion of the stent on follow-up. Result : The obstructive sites of thenasolacrimal system were junction level of the lacrimal sac and nasolacrimal duct(80%), common canaliculi(10%),and nasolacrimal duct(10%). In seven cases, we failed to insert the nasolacrimal stent. Four of the seven caseshad a history of previous operation on paranasal sinus or nasolacrimal system. At 4 weeks follow up, epiphoraredeveloped in four of 10 cases(reobstruction rate, 40%). Inflammatory process around the nasolacrimal duct stentwas conndered to be the cause of reobstruction in two of the four reobstructed cases. Conclusion : Success rate ofnasolacrimal duct stent insertion was 73%, and failure rate was 27%. The causes of the stent insertion failureincluded fibrosis and granulation tissue due to the previous operation around nasolacrimal duct system andparanasal sinus area. Inflammatory process around the stent caused recurrent obstruction.