if you mean modes of a nickname in a channel, you can try $nick(#,nick/number).pnick. Examples:
$nick(#,landonsandor).pnick $nick(#,1).pnick
If you mean what their server usermodes are, unless you're an IRCop (Im not one so Im guessing here) or running the server they're connecting to, you can't
Hi Powerkiting, I'm not exactly sure what it is your are trying to do, but if you are trying to see if a user has mode +v for example in a channel you are on thats easy enough, however if you are trying to see what modes (like +i) a user has when they join your channel that I dont think is possible. But as often happens, I could be wrong. heh!
Can you give a little more detail, like what server your trying this on and what exactly your trying to do?