OBJECTIVE: To identify the best mode for diagnosing and treating the patients with choledochal cysts. METHODS: A retrospective study was performed with medical records of patients diagnosed with choledochal cysts from January 1994 to December 2017. In all cases, the diagnosis was based on ultrasound examination. All the patients underwent cyst resection and were divided in two groups: bile enteric anastomosis in the high portion of the common hepatic duct or in the dilated lower portion. RESULTS: Eighty-one cases were studied. The age of presentation was 4 y 2 mo ± 4 y 1 mo, and the age for the surgical treatment was 5 y 5 mo ± 4 y 6 mo. In 61 cases, US was the only image examination performed. There were 67 cases of Todani type I (82.7%), 13 cases of type IV (16.0%) and one case of type III (1.2%). Nine patients (29.0%) in the first period and 2 patients (4.0%) in the second period presented with postoperative complications (p=0.016). CONCLUSION: In patients with choledochal cysts, US is the only necessary diagnostic imaging. Performing the bile enteric anastomosis in the lower portion of the common hepatic duct is safer and has a lower risk of complications.