If you only want to see the Sistine Chapel
 

And not all the Vatican Museum and gardens, it is possible to get tickets only for that? Where would I buy tickets before I go?

i think you need to buy tix for the museum also, but try to walk counter to the directions that weave you through. we passed by everyone else and arrived very early before the crowds- it was wonderfully quiet and serene...the next visit we followed the crowd...ugh,,,

The Vatican Gardens are a seperate tour from the Museums and Sistine Chapel. There is no Sistine Chapel only ticket. You must purchase the 10 Euro Museum ticket and then you are free to run through the Museum directly to the Sistine Chapel and see that only if you wish. Tickets cannot be purchased before you go unless you are buying a tour of the Musuems from one of the companies like Scala Reale.

Can you buy a ticket before you go in Rome? I am trying to figure out how not to stand in a long line for a ticket :)

As previously stated, the only way you can avoid the lines is to sign up for a tour. There are no individual advance tickets or reservations for the Vatican Museum.

Well darn it, it was worth a shot. I will go early or late in the day and hope for the best. I will be there at the 1st of Oct. so it shouldnt be terrible. I

We arrived before the museum opened in the a.m. and didn't have a long wait. Bonus of lines is that you sometimes meet and chat with great people, which we did at the Vatican Museum with a lovely girl named Madelyn from England.

Check out the website:
www.vatican.va
No lines at all!

In my recent experience, booking a Vatican Arts tour with Scala Reale does NOT get you an advance ticket to the Vatican museums. Scala Reale grous meet outside and proceed to buy their tickets and go through security screening like all other museum visitors. They schedule the tours to minimize time in waiting line -- e.g. entering the museum around 1 p.m. avoids the midmorning crunch but leaves ample time for a 3-hour visit. In late March, we had no wait outside for an afternoon entry. (A Scala Reale tour is very much worth every penny, even without a way to skip the lines.)

Just a word of caution... we went the first week in June 2002 and there was a very short line. I can't believe Oct. will be a problem. I virtually ran through the entire Vatican museum to see the Sistine Chapel (no small run!). When I got there, I realized I had ran past things that are very nice - maybe even nicer than the Sistene Chapel. I wish I had devoted more time to the museums and hadn't been so singularly focused.