Each item in a dialog window is described by a DLGTITEM data structure. This structure is rarely accessed directly by an application, since system functions handle most of the manipulation of dialog items. Applications that create dialog items that are not defined as part of a dialog-template resource must create dialog-window-item structures in memory.

A dialog window can have many items, so applications can use another structure, DLGTEMPLATE, to define the items. This structure consists of header information, followed by an array of dialog-window items. Applications that create dialog windows without using dialog resources must create a dialog template in memory, and, then, call the WinCreateDlg function.