We evaluated the relationship between clinical features and hypoxic-ischemic injury (HII) shown by diffusion-weighted MRI (DWI) in young children with head trauma, comparing inflicted trauma (IT) to accidental trauma (AT). This single-center consecutive cohort study included children age birth to 36 months admitted for head injury July 2001 to December 2004 with brain magnetic resonance imaging (MRI) obtained < or =1 week, identified from prospectively maintained registries of children with trauma. Clinical and radiological data during the hospital stay were extracted from medical records. MRIs were analyzed by study examiners blinded to clinical status and scored by type, severity and location of lesions attributable to traumatic, hypoxic-ischemic, or mixed injury patterns. 30 IT patients and 22 AT patients met inclusion criteria. IT cases were younger than AT, 3.0 versus 8.5 months. Mean time to MRI in IT (2.1 days) was similar to AT (1.9 days). HII was more common in IT (11 of 30) than AT (2/22, p = 0.03). Children with HII more commonly had seizures, needed intubation at presentation, and needed neurosurgical intervention compared to those without HII. Most patients with HII (10/14) required in-patient rehabilitation compared to those without HII (4/38). Our study is the first to characterize HII using diffusion-weighted MRI in young children, comparing IT and AT. The higher rate of HII on DWI-MRI in IT than in AT is likely multifactorial, involving respiratory insufficiency, seizures, and intracranial mass-occupying lesions requiring neurosurgical intervention. HII predicted need for in-patient rehabilitation in a large majority of children.