In our series of patients, we studied the incidence of residual cystic duct mucocele, which is still considered a rare complication in orthotopic liver transplantation (OLT). 152 OLTs were performed in 138 patients in the II Surgery Dept. of Bologna University, May 1986 to June 1994; a termino-terminal choledocho-choledochal anastomosis was performed in 145 of them. A choledocho-jejunal anastomosis was performed in other 7 patients. In 3 patients we observed an anechoic ovoidal structure localized just before the portal vein, near the main bile duct (MBD). Then, we monitored the evolution of this finding by ultrasonography (US), Doppler US, CT and CT-cholangiography. Integrated imaging, clinical and surgical data, led to the diagnosis of non-obstructive mucocele of residual cystic duct in OLT. To date, this complication has not led, on our series, to the necessity of new surgical procedures for cholestasis by MBD compression, which is in disagreement with literature data. In our series, the incidence of residual cystic duct mucocele is 2%, which is a higher value than those reported in the literature, suggesting that this condition be investigated carefully as a non-rare complication in OLT.