If you are creating the combobox, then Greg's approach works well, but seeing that he has improved on my suggestion, I'll return the favour.
I would set the combobox to display only the first column, by setting the column count (here 2, but you can have more colums as required) and making all but the first column have a width of zero. As it is a combobox and not a list box, I would also add a prompt at the top of the list and set the listindex to that prompt i.e. 0
Code:
Private Sub UserForm_Initialize()
With Me.ComboBox1
.ColumnCount = 2
.ColumnWidths = .Width & ",0"
.AddItem
.list(.ListCount - 1, 0) = "[Select City]"
.list(.ListCount - 1, 1) = ""
.AddItem
.list(.ListCount - 1, 0) = "Cleveland"
.list(.ListCount - 1, 1) = "A city in northwestern Ohio, USA"
.AddItem
.list(.ListCount - 1, 0) = "Cincinnati"
.list(.ListCount - 1, 1) = "A city in southwestern Ohio, USA"
.ListIndex = 0
End With
End Sub