We report a case of cytomegalovirus (CMV) pneumonitis that presented as a cavitary lung lesion in a patient with systemic lupus erythematosus receiving immunosuppressive treatment. The lesion was confirmed by positive polymerase chain reaction (PCR) for CMV in bronchoalveolar lavage fluid (BALF) and CMV antigenemia. PCR for CMV in BALF was demonstrated to be useful for the diagnosis of CMV pneumonitis on the basis of high sensitivity and specificity. After initiating ganciclovir, the lesion gradually regressed. A cavitary lung lesion associated with CMV is extremely rare. This presentation suggests that the differential diagnosis of cavitary lung lesion in immunocompromised individuals should include CMV.