The combined positron emission tomography/computed tomography scan is ideal in the initial staging of lymphomas and for evaluating the response to treatment. In posttreatment studies, the presence of a residual, metabolically active mass at the site of initially documented lymphoma is not expected to be anything other than residual active disease. We describe a case of intestinal non-Hodgkin's lymphoma that responded to chemotherapy but with a residual metabolically active mass at the site of initial disease. This mass was revealed to be a clinically silent closed intestinal perforation with abscess formation. Similar conditions should be kept in mind during the interpretation of posttreatment combined positron emission tomography/computed tomography scan and before exposing the patient to additional chemotherapy.