A DCM file is an image file saved in the Digital Imaging and Communications in Medicine (DICOM) image format. It stores a medical image, such as a CT scan or ultrasound. DCM files may also include patient information to pair the image with the patient.

The DICOM format was created by the National Electrical Manufacturers Association (NEMA) as a standard for distributing and viewing medical images, such as MRIs, CT scans, and ultrasound images. You can open DICOM files with a variety of programs for Windows, macOS, and Linux, such as XnViewMP, GIMP, and MeVisLab. NOTE: DCM files may also be saved as .DICOM files.

A DCM file is a file saved in the catalog format used by DiskCatalogMaker, a file cataloging and organization program for the Mac. It contains a database of files stored on multiple discs that can be searched by filename and other attributes. DCM files may also be saved as .DCMF files, which are more common.

If you receive or find a DiskCatalogMaker DCM file, you can only open it in DiskCatalogMaker. There is no other program available that supports the format. DCM files are similar to .DCMD files but DCMD files support thumbnail images. You can convert a DCM file to a DCMD file by opening the file in DiskCatalogMaker, selecting File → Save As..., and then choosing to save as a DCMD file.