I'm assuming you have a two column value list here where the duplicate values are displayed in the second column when you are hiding the first column and or sorting on the second column...
Not without changing your value list so that the values are now longer duplicates. If you think about it, this is generally a good idea. If you see two options in your value list that are identical, ("Smith" appears twice, for example), the user has no way to tell which "Smith" is the the one that they want.
Your work around is to define a calculation field that merges data from more than one field so that this data is now always unique and can be used as the "column 2" data to help the user make the correct choice. You can define a calculation such as this:
LastName & ", " & FirstName & " " & Address
If you define this as an auto-entered calculation on a text field, you can also set up a Unique Values validation rule so that duplicates are caught and identified during data entry so that you wont have identical values in your value list.
Thanks for the very quick reply and useful info. You assumed correctly; The value list displays the last name and then the date of birth for the user to differentiate between the two "Smiths". I suppose I could try and concatenate the surname and date of birth as you mention. Thanks again.