Dialog boxes are either modal or modeless. A modal dialog box must be closed (hidden or unloaded) before you can continue working with the rest of the application. For example, a dialog box is modal if it requires you to click OK or Cancel before you can switch to another form or dialog box.

The About dialog box in Visual Basic is modal. Dialog boxes that display important messages should always be modal — that is, the user should always be required to close the dialog box or respond to its message before proceeding.