Early diagnosis of scapholunate interosseous ligament tears with distal radius fractures is likely important in treatment and outcome, but identification of these injuries has not been well explored. We asked whether there was a difference in the scapholunate interval between high-grade and low-grade tears of the scapholunate interosseous ligament in distal radius fractures, the best position of the wrists to identify any differences; we also asked what gap width accurately identified high-grade tears on fluoroscopic evaluation. We fluoroscopically evaluated the scapholunate gap in six different wrist positions and then performed arthroscopic examination in 45 distal radius fractures in 44 consecutive patients. The tears were classified as high-grade (Grade 3 or greater) or low-grade (Grade 2 or less) based on arthroscopic findings. We then compared the scapholunate gap measured on fluoroscopic images between the high-grade tear group and the low-grade tear group and between the different positions of the same wrist. The scapholunate gap was wider in the high-grade tear group than in the low-grade tear group and wider in ulnar deviation than in radial deviation. A 2-mm scapholunate gap appeared the best cutoff point for the fluoroscopic diagnosis. We concluded fluoroscopic examination is a good test for identifying high-grade tears of the scapholunate interosseous ligament in distal radius fractures.