Unless of course it's two different directories on different devices which just happen to have the same inode number . . .

$ df -k | head -3; perl -le 'print"$_:\t".(stat $_)[1]for@ARGV' / /dev
+  
Filesystem              1K-blocks     Used    Avail Capacity  Mounted 
+on
/dev/disk0s9             58598824 39199392 19143432    67%    /
devfs                          96       96        0   100%    /dev
/:      2
/dev:   2
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Update: To elaborate, you want to use the tuple (device number, inode number), not just inode number.