The aim of this study was to report the treatment effectiveness of primary probing in children with congenital nasolacrimal duct obstruction (CNLDO) and describe the factors relating to the failure of the procedure. This was a retrospective study of 62 patients: 68% female. Mean age at probing was 27.26±19.15 months. Total success rate after first probing was 77.3% with median follow-up of 15 months. Total success rate after two probings was 90.9%. Complications were noted in 2.2%. The authors conclude nasolacrimal probing is a safe and effective means of restoring nasolacrimal flux in young children. Further evaluation needed for unresponsive patients because of adenoidal hypertrophy may be associated with probing failure. Success rate of nasolacrimal duct probing was not related to age, gender, laterality or surgeon’s experience.