It's an Italian restaurant located in the street that runs up the hill straight from the Seatran pier. After about 500 meters or so it's on your right hand side.
They serve some excellent Italian food here and I find myself visiting more often whenever I am visiting Koh Tao.
This is how the place looks like from the outside, not very hard to find. It has a very nice laid back atmosphere and it invites just to sit back and enjoy your meal.