Fourteen patients with spinocerebellar degeneration (SCD) were subjected to MRI and PET studies. The quantitative MRI data revealed significant cerebellar and pontine atrophy in the patients with olivopontocerebellar atrophy (OPCA), and cerebellar atrophy in the patients with late cerebellar cortical atrophy (LCCA). We failed to demonstrate significant differences in the pons between LCCA patients and normal controls. PET measurements revealed decreases in cerebral oxygen metabolic rate (CMRO2) in the cerebellar hemisphere and vermis in both groups of patients. The markedly decreased cerebral blood flow (CBF) and CMRO2 in the pons were found only in the patients with OPCA. PET data corrected for the tissue shrinkage on the basis of MRI morphometry indicated a net reduction in cerebellar CMRO2 and CBF. The present study has demonstrated that a combination of functional and anatomical data offers further evidence in favour of the current acceptable classification of SCD based on clinicopathological grounds. Our data further suggest that the amount of atrophy in the cerebellum could not fully account for the decreased metabolic rates observed in PET studies.