Purpose Crossed cerebellar diaschisis (CCD) has been widely studied in hemispheric stroke but is less characterized in epilepsy. In this study, we used F-18-FDG PET/CT to investigate the risk factors for CCD and its prognostic value for intractable epilepsy caused by focal cortical dysplasia (FCD). Methods One hundred medically intractable epilepsy patients pathologically diagnosed with FCD postoperatively were included and classified into two groups: CCD+ and CCD-. PET/CT images were analyzed qualitatively by visual assessment and semi-quantitatively using the absolute asymmetry index (|AI|). Clinical factors, including age, sex, body mass index (BMI), age at seizure onset, epilepsy duration, seizure type, seizure frequency, electroencephalography (EEG) and brain magnetic resonance imaging (MRI), were retrospectively assessed from medical records. Follow-up outcomes were evaluated according to the Engel classification at 3, 6, 12, 24 and 36 months postoperatively. Results Of the 100 patients, 77 (77.0%) were classified as CCD-, and 23 (23.0%) were classified as CCD + . CCD+ patients had a higher number of lobes involved on PET (3.61 +/- 2.16 vs 2.26 +/- 1.01, P < 0.001) than CCD- patients. CCD- patients showed more negative MRI results than CCD + patients (P = 0.02). At 12 months postoperatively, 70.7% (29/41) of CCD- patients and 30.8% (4/13) of CCD + patients presented a favourable prognosis (P = 0.02). Significant differences in the average |AI| values in the posterior frontal and anterior temporal lobes were found between CCD+ and CCD- patients (P < 0.05). Conclusion The number of lobes involved on PET, structural anomalies on MRI, the |AI| values in the posterior frontal and anterior temporal lobes may be predisposing factors for CCD. CCD occurrence may help predict the prognosis of FCD patients at 12 months postoperatively.