Firewalled Flooding

[phantom rewt <titan () blader com>]

Hello ppl,

  First I'd like to thank Fyodor for his fucking cool job, nmap really
r0x. And thanks to everybody who supports it and this list.

  Second, I have a little doubt. Suppose I'm scanning a host, but it has
too much ports firewalled. The point is, I waste too much time when I
only really needed to know only the open ports. 

Question: Can I use nmap to scan ONLY open ports and ignore the filtered
ones? Is there such an option?

Thanks in advance,

Byez,

phantom rewt