To get unique vaues you just need to group the entries for the columns (that applies to all kind of queries, not only to "FOR XML" ones :hehe: ):

SELECT a.ID,

a.ColA,

STUFF((SELECT ',' + b.ColB AS "text()"

FROM @t b

WHERE b.ID = a.ID

AND b.ColA = a.ColA

GROUP BY b.ColB -- << here

ORDER BY b.ColB

FOR XML PATH(''),TYPE).value('.','VARCHAR(MAX)'),1,1,'') AS ColB,

STUFF((SELECT ',' + b.ColC AS "text()"

FROM @t b

WHERE b.ID = a.ID

AND b.ColA = a.ColA

GROUP BY b.ColC -- << and here

ORDER BY b.ColC

FOR XML PATH(''),TYPE).value('.','VARCHAR(MAX)'),1,1,'') AS ColC

FROM @t a

GROUP BY a.ID,a.ColA

ORDER BY a.ID,a.ColA;