I will be in Madrid by myself in a couple of weeks. I am sure I will eat lots of tapas, but I also wonder if restaurants are hospitable to single diners. Will restaurants take a reservation for one during busy lunch and dinner service? Is there a difference in policy between upscale and average restaurants? Is the attitude different during lunch than during dinner? Are there any recommendations?

I can't answer the question about reservations, although I never heard of them being used in Spain, but I can tell you that restaurantes have no problem with the appearance of a single diner. A few years ago, I was in Madrid for a month by myself (the last few trips my husband accompanied me). I went to eat...obviously, by myself. How did the restaurantes treat me? The same, if not better, than when I was accompanied. They seemed to want to take care of me. I didn't go to the same restaurante everyday...but did once a week. So, the waiters got to know me and treated quite well.

Sheryl

Ress - you will have no problem with requesting and getting a table for one person. I just can back from a 10-day trip and had no problems.
If you want to ensure getting a table then I would suggest that you get there BEFORE the Spanish do.
So, for example at lunchtime, if you can be at a restaurant for 1330, you will have a better chance of gettting a table than you would have at 1400 or 1430.
The same goes for eating at night. Try to get there between 2100 and 2130. The Spanish will be be heding for the restaurant between 2130 and 2200.
Enjoy your visit.
Robbieroy

Ress:You are in for a very pleasant surprise. You will find that service is the name of the game, and I would be surprised to find out you run into one surrley waiter. Don't be nasty to them, and I think you will find them very accomodating. Remember it is Madrid that you are going to, not Paris or New York City.

You will not find this a problem. There are plenty of solteros in town and you'll find yourself with plenty of other single men (mainly older) in neighborhood restaurants.

As a previous poster said, it might be wise to turn up earlier than the Spaniards do. As your eating schedule will be earlier than the one Spaniards are used to, this should not be changing your usual habits one bit.

Enjoy your trip!

I don't think you're going to be treated different just because you dine alone. Waiters wages don't depend on tips and they are going to earn the same money whether they serve a 8 people table or a solo dinner.

You will probably find much more solo diners at lunch (probably a "menu del día" on their lunch break at work).