Scapula fractures can be very difficult to characterize on both plain radiographs and CT-scans. Currently there are no standardized, systematic techniques for measuring displacement in these fractures. We describe five parameters for measuring displacement in extra-articular scapula neck and body fractures and test the inter- and intraobserver reliability of these techniques using plain radiographs and 2D- and 3DCT scans. Three observers evaluated forty-five consecutive injury radiographs, and 2D+ 3D-CT of patients with a scapula neck and/or body fracture. Techniques for measuring medial/lateral displacement, angulation, translation, glenopolar angle, and glenoid version were developed. Two trials were performed 6-weeks apart. Mean across-trial interobserver reliability was the same or higher for 3D-CT in all parameters when compared to plain radiographs. Intraobserver reliability was not systematically higher for one modality. For both radiographs and 3D-CT, interobserver reliability was highest for glenopolar angle (ICC = 0.66 and 0.85, respectively) and lowest for medialization (ICC = 0.43 and 0.50), respectively. Intraobserver reliability was greatest for medial/lateral displacement (Pearson r = 0.75) and lowest for translation (Pearson r = 0.60) when performed on radiographs and greatest for glenopolar angle (Pearson r = 0.89) and lowest for translation (Pearson r = 0.64) when performed using 3D-CT. Both individual and pooled measurements for angulation and GPA were significantly higher on 3D-CT versus radiographs. Here we define, standardize, and validate parameters for measuring scapula fracture displacement on radiographs and CT. Our results show that 3D-CT is more reliable than plain radiography in the assessment of scapula fracture displacement. We recommend utilization of 3D-CT if fracture displacement warrants surgical consideration.