BACKGROUND: Cystic lesions of the liver consist of a heterogeneous group of disorders and may present a diagnostic and therapeutic challenge. Large hepatic cysts tend to be symptomatic and can cause complications more often than smaller ones. STUDY DESIGN: We performed a retrospective review of adults diagnosed with large (≥4cm) hepatic cystic lesions at our center, over a period of 15 years. Polycystic disease and abscesses were not included. RESULTS: Seventy-eight patients were identified. In 57 the lesions were simple cysts, in 8 echinococcal cysts, in 8 hepatobiliary cystadenomas, and in 1 hepatobiliary cystadenocarcinoma. In four patients, the precise diagnosis could not be ascertained. Mean size was 12.1cm (range, 4 to 30cm). Most simple cysts were found in women (F:M, 49:8). Bleeding into a cyst (two patients) and infection (one patient) were rare manifestations. Percutaneous aspiration of 28 simple cysts resulted in recurrence in 100% of the cases within 3 weeks to 9 months (mean 4 1 2 months). Forty-eight patients were treated surgically by wide unroofing or resection (laparoscopically in 18), which resulted in low recurrence rates (11% for laparoscopy and 13% for open unroofing). Four of the eight patients with echinococcal cysts were symptomatic. All were treated by open resection after irrigation of the cavity with hypertonic saline. There was no recurrence during a followup period of 2 to 14 years. Hepatobiliary cystadenomas occurred more commonly in women (F:M, 7:1) and in the left hepatic lobe (left:right, 8:0). Seven were multiloculated. All were treated by open resection, with no recurrence, and none had malignant changes. Cystadenocarcinoma was diagnosed in a 77-year-old man, and was treated by left hepatic lobectomy. CONCLUSIONS: Large symptomatic simple cysts invariably recur after percutaneous aspiration. Laparoscopic unroofing can be successfully undertaken, with a low recurrence rate. Open resection after irrigation with hypertonic saline is a safe and effective treatment for echinococcal cysts. Hepatobiliary cystadenomas have predilection for women and for the left hepatic lobe. Malignant transformation is an uncommon but real risk. Open resection is a safe and effective treatment for hepatobiliary cystadenoma, and is associated with a low recurrence rate.