Have you tried Feebreeze yet (however it is spelled)or maybe a local drycleaner has a product you could put on or more advice.Would be a good place to start.

You could also try sprinkling a carpet air freshener powder straight on the mattress. I'd advise getting the pet odor one as it's the strongest. Arm and Hammer make the best one's [IMO] and you just leave it on for half an hour to an hour and vacuum it off again.

You could also Febreeze it after [not before as it's a spray and the powder will stick and make a big mess, lol]. You'll also want to do the box spring as well.

If you find, for some reason, that the smoke smell is still lingering in the room, and you have no aversions then try lighting a candle or some nice incense. Daubing some of your favourite perfume or cologne on a light bulb will make your room smell great when the light is on. A couple of drops on the bottom of the bulb [where it says the wattage as it's the hottest part of the bulb] works wonders, but make sure the bulb is completely cold! I tried it once before the bulb was completely cooled down and it basically blew up. If I didn't have to wear glasses, I'd've been making an emergency trip to the hospital that day.