nmap options

If all my ports are closed and someone does an 'nmap -sU -sT' scan on me and shows unfiltered ports. Could it be true, or is it just a false output? I heard somewhere that doing both of those options maybe give you false output, so im asking here ;) __________________________________________________ Terrorist Attacks on U.S. - How can you help? Donate cash, emergency relief information http://dailynews.yahoo.com/fc/US/Emergency_Information/