How far in advance do you need reservations?we will be arriving at noon on Sunday. Was wondering if we could visit that afternoon. Thanks!

It's easy and convenient to make your reservations online before you leave for your trip; then you need only pick up your tickets about 30 minutes before your scheduled entry.

We've always reserved at least two weeks in order to get the time we want. Sunday is popular and does sell out, as space for each viewing is limited, so I would personally not wait any longer to make reservations.

Only the Borghese can advise whether or not the time/date you had in mind is still available.

KKBay
Another option is to phone the Borghese directly to make a reservation. They have a english option on the telephone. That's what I did - no problem. I just returned from Rome a few days ago. Went to Borghese Gallery on a Sunday - it was sold out.
Gohedwig

We arrived in Rome without reservation to the Gallery. We spent an afternoon in the park by the museum then made our way inside to make reservation for 2 days from then.

sandi was lucky. I would do it before leaving home. I have been there twice (once in March, once at Christmas time), and both times they were completely sold out for the next 5-7 days.

Last month I was at the Borghese Gallery. I had made my reservations about 3 weeks in advance. When I got there (Thursday) there were signs posted that there wasn't any available space until the following Tuesday so you should get your tickets now and not wait.

I was there a couple of weeks ago. I'd bought the Roma Pass and intended to use the free admission but found that the first day for which I could get a reservation was the day after the Pass expired--it is only valid for 3 days.

Just called and emailed. All sold out for Sunday. I'm trying for Tuesday.
Thanks for info.
BTW, it's our first trip to Italy and will be on a tour for a little over two weeks w/ hubby and 18 year old son. Will post info later.