The prognostic value of the apparent diffusion coefficient (ADC) for diffuse myocardial fibrosis and its relationship to the contractile function is still not investigated. A total of 45 HCM patients and 20 controls underwent a 3.0-T cardiac magnetic resonance imaging (CMRI), including cine, T1 mapping, and DWI. ADC values in the ECV ≥ 29.6% group were significantly increased compared to the ECV < 29.6% group. ADC values were linearly associated with 3D LV GCS, GLS, GCSR, GLSR and GRSR. Impairment of contractile function in HCM is predominantly associated with the contrast-free ADC value.