Why doesn't this work:

Private Sub CommandButton1_Click()
If ListBox1 = "" Then
MsgBox ("True")
Else
MsgBox ("False")
End If
End Sub

While this does:

Private Sub CommandButton1_Click()
If ListBox1 < "" Then
MsgBox ("True")
Else
MsgBox ("False")
End If
End Sub

or have I missed something embarrassingly obvious?
Cheers Wobbly.