We examined the relation between cigarette use and occurrence of delayed union and nonunion after ulna-shortening osteotomy for ulnar impaction syndrome. After obtaining the smoking history of 39 patients (40 wrists), we found that, compared with nonsmokers, smokers experienced longer healing times and more of them experienced healing delay and nonunion. Mean union rates were 7.1 months in smokers and 4.1 months in nonsmokers. Six smokers (30%) and no nonsmokers experienced delayed union or nonunion. Given the adverse effects of smoking on bony union, we recommend that smoking history be considered when selecting patients for ulna-shortening procedures.