The purpose of this study is to report the role of whole-body 2-[¹⁸F] fluoro-2-deoxy-D-glucose (FDG) positron emission tomography fused with computed tomography (PET/CT) after immunocytochemical and clonal diagnosis of intraocular lymphoma with vitrectomy cell blocks. Eleven patients with intraocular lymphoma were involved in this study : 6 patients presented with vitreous opacity in both eyes and 5 patients presented with unilateral involvement. The concurrent retinal lesions were present in 6 eyes of 5 patients. Brain lymphoma was diagnosed in 7 of the 11 patients : simultaneous with eye lesions in one patient, following the eye lesions in 3, and prior to the eye lesions in 3. Vitrectomy was done in 17 eyes of the 11 patients, and vitrectomy cell blocks were processed for immunocytochemical staining and clonality analysis by polymerase chain reaction amplification of the immunoglobulin heavy chain gene. The 7 most recent patients were evaluated with fluorodeoxyglucose whole-body PET/CT. Immunocytochemical staining of vitrectomy cell blocks in all patients showed large cells which were positive for CD20 and Ki-67 but negative for CD3, consistent with diffuse large B-cell lymphoma. The size and sequence of amplified fragments of the immunoglobulin heavy chain gene were different between the lesions of both eyes in one patient while they were the same in another patient. PET/CT after the diagnosis by vitrectomy revealed abnormal uptake in the cerebellum of two patients, in the eye as a recurrent lesion of one patient, and in both eyes as residual retinal lesions of one patient. In conclusion, PET/CT could be considered as a method to confirm brain lymphoma or as a reference for initiating additional therapy in the case of eye recurrence or residual lesions after vitrectomy. The clonality of lymphoma cells was variable between the lesions in both eyes. [J Clin Exp Hematopathol 49(2) : 77-87, 2009]