To establish the association between the obstruction site, whether it is unilateral or bilateral, age group, and sex.A retrospective observational study of 1000 lacrimal ducts of 500 consecutive patients seen in the Emílio Amorim Radiological Clinic, who were suspected of having lacrimal duct obstructions, was performed.Of the studied patients, 121 were men and 379 were women. Their ages varied between 2 years and 93 years. 148 of the examinations were normal; in 298 the obstructions were unilateral and in 54 they were bilateral. The majority of the obstructions occurred at the valve of Krause. There was a significant difference in the correlation of the obstruction site with sex. The obstruction was total in 378 valves and partial in 28. Other findings included sinusitis, osteomas, bone fractures, fistulae, diverticulum, and lacrimal stones.Obstruction of the lacrimal ducts is normally total, unilateral, and sited at the valve of Krause. The obstruction of this valve predominantly affects women, whereas obstruction of the valve of Hasner mainly affects men. There was no significant difference in the distribution of obstructions by age group.