There is provided an image forming system that are capable of preventing a user or operator from forgetting to carry out a maintenance operation based on required sub-maintenance items after execution of a maintenance operation based on an associated maintenance item, such as component replacement, cleaning, or adjustment. A table of maintenance items and sub-maintenance items associated with respective ones of the maintenance items is stored in a ROM. When a CPU determines that a maintenance operation based on a selected one of the maintenance items has been completed, the CPU determines whether or not there is any sub-maintenance item associated with the selected maintenance item, by referring to the table. When it is determined that there is one or more sub-maintenance items associated with the selected maintenance item, a CPU provides control to display the sub-maintenance item or items in an operating/display unit.