Chairman and Chief Executive Bruce Henderson is taking a leave of absence to pursue medical treatment for a malignant tumor.
The condition was first diagnosed last August. The company said its board named Chief Operating Officer Frank Russomanno acting CEO while Henderson is away.
Imation makes removable data-storage products. Henderson has been the company's chairman and CEO since May 2004.
"I'm grateful for the warm messages of support I've received since I started treatment last August. Now I've made the decision to focus my energy at this time on my health and my medical treatment," Henderson said in a statement Thursday.