PURPOSE: To determine through an analysis of the location of pleural effusion associated with ascites, as seen on abdominal CT scan, differences in the distribution of pleural effusion according to the etiology and distribution of ascites. MATERIALS AND METHODS: We retrospectively evaluated 77 consecutive patients in whom abdominal CT scan revealed pleural effusion associated with ascites. Patients with history of surgery or trauma and those with clinically and radiologically diagnosed lung or pleural diseases were excluded. We compared the location of pleural effusion with the etiology and distribution of ascites. RESULTS: Forty-two patients were suffering from hepatobiliary diseases, mainly right dominant pleural effusion (26/42, 62%). Fourteen had intraperitoneal carcinomatosis with no significant difference between the frequency of right dominant (5/14, 36%)and of left dominant (6/14, 43%) pleural effusion. Eleven patients had pancreatic diseases, with mainly left dominant pleural effusion (6/11, 55%). Patients with right dominant ascites usually had right dominant pleural effusion (22/24, 92%) and those with left dominant ascites had left dominant pleural effusion (9/10, 90%). CONCLUSION: Ascites-associated pleural effusion correlated with the anatomical location of the etiology of ascites ; its laterality was, in addition, usually the same as that of ascites.