Crossed cerebellar diaschisis(CCD) involves reduced metabolism and blood flow in the cerebellar hemisphere contralateral to a supratentorial lesion. ASL is a valuable tool for quantifying regional cerebral blood flow. This study assesses ASL-MRI's ability to detect CCD in epilepsy using integrated 18F-FDG PET/MRI and compares ASL with PET images in evaluating CCD. 74 patients with drug-refractory epilepsy who underwent integrated 18F-FDG PET/MRI pre-surgery and CT/MRI post-surgery was analysed. Regions of interest were outlined on MRI images and simultaneously transferred to PET and ASL images. CCD detection was evaluated visually and semi-quantitatively using the absolute asymmetry index (AIabs). Out of 74 patients, PET detected CCD in 24 (32.43%) and ASL in 18 (24.32%), with no significant difference between them (P = 0.274). Based on the PET results, the ROC curve for ASL's diagnostic accuracy for CCD showed an area under the curve of 0.69 (P = 0.008), an accuracy of 75.68%, a sensitivity of 50%, a specificity of 88%, a positive predictive value (PPV) of 66.67%, and a negative predictive value (NPV) of 78.57%. Four CCD types were identified: both PET and ASL positive (16.22%), PET positive and ASL negative (16.22%), ASL positive and PET negative (8.10%), and both negative (59.46%). AIabs correlation was positive between PET and ASL in the epileptic zone (r = 0.658, P < 0.001) and cerebellum (r = 0.407, P < 0.001). In ASL CCD-positive cases, AIabs showed a negative correlation between the epileptic zone and cerebellum (r=-0.581, P = 0.011), while in both PET and ASL CCD-positive cases, AIabs correlation was positive (r = 0.670, P = 0.017). ASL can be used as a method for evaluating CCD, and when combined with FDG-PET, it can further enhance its diagnostic accuracy for CCD. In CCD-positive cases, a notable discrepancy was observed: no correlation in PET images but a correlation in ASL images between the supratentorial epileptic zone and contralateral cerebellar hemisphere, indicating CCD might be linked to regional cerebral blood flow changes.© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.