This study assessed whether nonunion of displaced scaphoid waist fractures with nonoperative treatment could be predicted from 4 week CT scans. Thirty-one patients with unilateral displaced scaphoid waist fractures and adequate follow-up were included. CT scans in the longitudinal axis of the scaphoid with sagittal and coronal slices were done 4 weeks after the index injury. The effects of fracture gap, sclerosis and bone resorption on union were assessed. Fracture union was observed in all 13 displaced fractures with a < 2 mm gap, four of the seven with a gap of 2-3 mm and only four of the 11 with a gap > 3 mm (p = 0.01). Bone resorption involving more than 50% of the fracture cross-section was also associated with nonunion, but sclerosis was not.