Madisson is a cafe in the Radisson SAS hotel in the centre of Tallinn. It's expensive, but the food is more or less OK. Madisson is usually quite empty, so you can enjoy a little privacy, except in breakfast or lunchtime. The waitresses are friendly, but sometimes quite disturbing, coming to the table very often trying to sell you more and more..
Interior looks like a ship-restaurant to me. Not that there's anything wrong with it, just the furniture and it's quite a big as well.
I wouldn't go there if I had other choices. Just a few steps away is CityGourmet, a much nicer place to have a tea or coffee and a small snack.