The high frequency of benign and asymptomatic liver cysts must not underevaluate the potential diagnostic difficulties of liver cystic diseases. Complicated liver cyst or cystic mass of various origin, such as developmental, neoplastic or inflammatory, are important to be recognized by the radiologist. The diagnostic approach is depending on the number of lesions and their dissemination. The presence of a wall, the internal structure of the lesion, particularly the MR signal and the proximity of the biliary tree are the main diagnostic criteria. Some less frequent but characteristic unusual features need to be memorized.