Background: Hepatobiliary cystadenomas and cystadenocarcinomas are rare and often misdiagnosed. Aims: We report our experience with 33 cases over 20 years to discuss an algorithm for these diseases. Methods: Patients presenting with a diagnosis of hepatobiliary cystadenomas and cystadenocarcinomas were retrospectively reviewed from January 1991 to October 2010. Clinical data were collected by examining hospital records and by follow-up questionnaire interviews. Results: Thirty-three patients had pathologically diagnosed hepatobiliary cystadenomas (19/33, 17 females and two males) or cystadenocarcinomas (14/33, five females and nine males). Symptoms of cystadenomas at hospitalization were abdominal bloating or pain (9/19). Nine patients had an elevated level of carbohydrate antigen (CA) 19-9. The surgical procedures, i.e. cyst enucleation, segmentectomy, sectionectomy and hemi-hepatectomy, were performed with satisfactory outcomes. Symptoms of cystadenocarcinomas included abdominal bloating or pain (8/14) and fever (3/14). Seven patients had elevated CA19-9. The imaging characteristics of cystadenocarcinomas were similar to those of cystadenomas. The clinical outcomes for cystadenocarcinomas were mostly poor after either surgical or conservative treatment. Conclusions: Clinical symptoms are unreliable for these diagnoses and their differential diagnosis. Imaging evaluations and CA19-9 are of value for the recognition of cystadenoma and cystadenocarcinoma, but not for their differential diagnosis. Any recurrence of liver cyst after surgery or other treatments should lead one to suspect one of these diseases. Invasive examination and percutaneous fine-needle aspiration cytology are not recommended. Complete excision or careful enucleation should be the first treatment choice for a better prognosis.