DISTINCT not needed to count total number of forum posts

PostgreSQL shows that this query executes in 131ms:
2009-03-13 17:23:48 CET LOG: durée : 131.722 ms, instruction : SELECT COUNT(DISTINCT(nid)) FROM forum

SELECT COUNT(nid) FROM forum
executes in 67ms (twice left)

Both queries result in 67497. So I guess distinct is not needed (although I cannot be sure).