Cytotoxic lesions of the corpus callosum (CLOCCs) have broad differential diagnoses. Differentiating these lesions from lesions of vascular etiology is of high clinical significance. We compared the clinical and radiological characteristics and outcomes between vascular splenial lesions and CLOCCs in a retrospective cohort study. We examined the clinical and radiologic characteristics and outcomes in 155 patients with diffusion restriction in the splenium of the corpus callosum. Patients with lesions attributed to a vascular etiology (N = 124) were older (64.1 vs. 34.6 years old, p < 0.001) and had >1 vascular risk factor (91.1% vs. 45.2%, p < 0.001), higher LDL and A1c levels, and echocardiographic abnormalities (all p ≤ 0.05). CLOCCs (N = 31) more commonly had midline splenial involvement (p < 0.001) with only splenial diffusion restriction (p < 0.001), whereas vascular etiology lesions were more likely to have multifocal areas of diffusion restriction (p = 0.002). The rate of in-hospital mortality was significantly higher in patients with vascular etiology lesions (p = 0.04). Across vascular etiology lesions, cardio-embolism was the most frequent stroke mechanism (29.8%). Our study shows that corpus callosum diffusion restricted lesions of vascular etiology and CLOCCs are associated with different baseline, clinical, and radiological characteristics and outcomes. Accurately differentiating these lesions is important for appropriate treatment and secondary prevention.