A DICOM SOP class is a combination of a DICOM service command (DIMSE) and an information object, or a Service Object Pair (SOP). The composite service commands services start with the letter C.

The Composite commands are:

• The C_Store, to request to exchange a composite SOP instance, such as an image. This can be considered a "push".
• The C_Find, to match a series of attributes against the attributes of the SOP instances managed by another DIMSE-service-user, such as those used by a workstation to query an archive. The C_Find service returns for each match a list of requested attributes and their values.
• The C_Get, to fetch the information for one or more composite SOP instances, such as. to retrieve images from an archive by a workstation. This service can be considered as a pull.
• The C_Move, to move the information for one or more composite SOP instances from a peer DIMSE-service-user to a third party, based upon the attributes supplied by the invoking DIMSE-service-user (like those used by a router to prefetch images from an archive to a workstation.)
• The C_Echo, to verify end-to-end communications with a peer DIMSE-service-user, like those used by service engineers for troubleshooting to verify whether one can connect and communicate with another application entity.

The composite commands operate on objects that are composed of several real world entities. A good example is an image, a composite object that contains information about the patient (name, ID, birth date, sex), equipment it was generated from (manufacturer, model number), the study it belongs to (Study ID) and the pixel data itself.