Just run the same query but comment out the where clause in the base part of the rCTE.

WITH rCTE AS(

SELECT CAST( CAST( ParentID AS varchar(10))+ '/' + CAST( ChildID AS varchar(10)) AS varchar(8000)) AS String,

ParentID,

ChildID

FROM Hierarchy

--WHERE ParentID = @Value

UNION ALL

SELECT CAST( r.String + '/' + CAST( h.ChildID AS varchar(10)) AS varchar(8000)) As String,

h.ParentID,

h.ChildID

FROM Hierarchy h

JOIN rCTE r ON h.ParentID = r.ChildID

)

SELECT String

FROM rCTE r

WHERE NOT EXISTS( SELECT *

FROM rCTE x

WHERE x.String LIKE r.String + '%' --Contains the string

AND x.String > r.String) --And is larger than the string

ORDER BY String