The goal of this study was to evaluate whether the values of ADC in spondylarthritis axial active inflammatory lesions are different from ADC values in type 1 Modic changes.95 patients with recent lumbar pain, including 46 patients with diagnosed or suspected spondylarthritis and 49 patients with purely degenerative history, underwent spine MRI. T1w, STIR, and diffusion-weighted images (DWI) were obtained. Two musculoskeletal radiologists interpreted the images. Axial active inflammatory lesions from the SpA group and type 1 Modic changes from the degenerative group were identified on T1w and STIR sequences. ADC values from these lesions and from healthy subchondral bone were compared.All axial active inflammatory lesions (n=27) and type 1 Modic changes (n=22) identified in T1w and STIR images were visible on DWI. ADC values were significantly higher (p<0.05) for axial active inflammatory lesions (median=0.788×10 −3 mm 2 /s, IQR 25–75 [0.7×10 −3 mm 2 /s; 0.9×10 −3 mm 2 /s]) than for type 1 Modic changes (median=0.585×10 −3 mm 2 /s, IQR 25–75 [0.55×10 −3 mm 2 /s; 0.60×10 −3 mm 2 /s]) and normal subchondral bone (median=0.443×10 −3 mm 2 /s, IQR 25–75 [0.40×10 −3 mm 2 /s; 0.50×10 −3 mm 2 /s]). Intra-class correlation coefficients for intra- and inter-reader ADC values comparison were excellent (0.89 and 0.98 respectively).DWI is a sensitive and fast sequence that offer the possibility of quantifying diffusion coefficients of the lesions, which could help to discriminate between spondylarthritis axial active inflammatory and type 1 Modic changes.