The ComboBox control was never implemented with the intention to support multiple selection, however this was recently discussed by the UX team. The conclusion of this discussion was that supporting multiple selection should not be a part of the ComboBox control, but instead be a separate control, commonly referred to as a 'ListBox'.

Because of this conclusion, a major API oversight was also identified in that the ComboBox selectionModel property. The issues is that this is of type SelectionModel, rather than SingleSelectionModel. This means that developers will assume that multiple selection is supported, when in fact it is not (and there are no intentions of supporting this). If this bug in the API is not resolved prior to ComboBox shipping in JavaFX 2.1, the ComboBox selectionModel API must always be of type SelectionModel, which will lead to confusion and / or bug complaints from developers expecting functionality.