Auto_inc field and stored procedure

CREATE PROCEDURE `sp_SaveComment`(IN nCommentID int, IN nUserID INT, IN dCreateDate datetime, IN sContent text)
BEGIN
if nCommentID = 0 then
    Insert into comments(UserID, CommentDate, Content) Values(nUserID, dCreateDate, sContent);

    /* NOTE: CommentID is an AUTO_INC field. Following line does not get the new CommentID value
    Select nCommentID = LAST_INSERT_ID(); /*CommentID from comments order by CommentID Desc Limit 1;*/

    insert into KeywordProcess(CommentID, Action) Values (nCommentID, 'A');
else
    Update comments set Content = sContent Where CommentID = nCommentID;
    insert into KeywordProcess(CommentID, Action) Values (nCommentID, 'U');
end if;

select nCommentID as 'CommentID';

END

Select nCommentID = LAST_INSERT_ID(); 

Select LAST_INSERT_ID() INTO nCommentID