not if you unmask it. you can do ip re-directs on your router config to point to your computer's lan ip address when the wan ip address is accessed. then all you need is your wan address and you should be able to host games.
if you do indeed do as elpha says and place yourself as the DMZ host, then you would just need your wan address.
**note: wan - wide area network; lan - local area network
the wan address is the ip address that your isp gave your account. if it's static, then it should be in your paperwork. if it's dynamic, you'd have to run to sites such as
http://www.dslreports.com/whois to find your wan ip address. note also, that this bein dynamic, it has the potential to change.
the lan address is the 192.168.xxx.xxx number your computer has that was given it by the router. to find that, you could do the following:
if running win9x, Start > Run > "winipcfg" ; in the drop down box, highlight your network card and your info should be there.
if running win2k or winxp, Start > Run > "cmd" ; once in the command prompt, type 'ipconfig' hit enter and it should be listed there too.
but realize also that your router is set to give you a lan ip address dynamically and can change as well. to be on the safe side, manually assign an ip address to your computer, making sure it's in the same subnet as your network, ie. if the other computers are 192.168.1.100 and the subnet mask on your router is 255.255.255.0, then only change the last 3 digits, keeping the previous 3 sets the same 192.168.1.xxx.
sorry if this is alot. but good luck