BACKGROUND: Prior studies have shown a correlation between the National Institutes of Health Stroke Scale (NIHSS) and stroke volume on diffusion weighted imaging (DWI); data are more limited in patients with minor stroke. We sought to determine the association between DWI lesion(s) volume and the (1) total NIHSS score and (2) NIHSS component scores in patients with minor stroke. METHODS: We included all patients with minor stroke (NIHSS 0–5) enrolled in the Stroke Warning Information and Faster Treatment study. We calculated lesion(s) volume (cm3) on the DWI sequence using Medical Image Processing, Analysis, and Visualization (MIPAV, NIH, Version 7.1.1). We used nonparametric tests to study the association between the primary outcome, DWI lesion(s) volume, and the predictors (NIHSS score and its components). RESULTS: We identified 894 patients with a discharge diagnosis of minor stroke; 709 underwent magnetic resonance imaging and 510 were DWI positive. There was a graded relationship between the NIHSS score and median DWI lesion volume in cm3: (NIHSS 0: 7.1, NIHSS 1: 8.0, NIHSS 2: 17.1, NIHSS 3: 11.6, NIHSS 4: 19.0, and NIHSS 5: 23.6, P <.01). The median lesion volume was significantly higher in patients with neglect (105.6 vs. 12.5, P =.025), language disorder (34.6 vs. 11.9, P <.001), and visual field impairment (185.6 vs. 11.6, P <.001). Other components of the NIHSS were not associated with lesion volume. CONCLUSION: In patients with minor stroke, the nature of deficit when used with the NIHSS score can improve prediction of infarct volume. This may have clinical and therapeutic implications.