Is it possible to take wheels from Volvo 740, size 205-55-15 and put them on Volvo 240 model that currently has wheels size 185-70-14 ?

Somewhere I have photo of 14, 15, and 16 inch wheels from 740s and a 17 inch wheel from an 855R - all have the same outside diameter!

In the case of each larger wheel, the tires are lower.

In the custom world, they call them original, +1, +2, and +3.

It's the TIRES that are 185, 205, etc. sized. Wheels are 14" x 5" or 15" x 6", for example. To the other excellent advice I'd add -- upsizing to the 15's is likely going to result in a heavier wheel/tire combo. I'm sure it will look better. And with a bit more rubber on the road (assuming the 740 tires on mounted on a proper width wheel) you may have a bit more cornering grip. The extra weight, however, has to be accelerated and controlled with stock springs/shocks. So depending on just how much heavier the new combo is, acceleration and fuel mileage, especially stop and go, will take a small hit. Perfect world - more damper to help control the extra weight.

Yes, all 700 and 900 series wheels will fit the 240 except for the very last S90 and V90 ones when they changed to a front wheel drive type wheel.

Luka

Yes the wheels will fit as Dave stated, but you can not use the lug nuts from the 740. The 740 threads are metric, the 240's are not. I mention this in case those new wheels are alloy with chrome lugs, you will need the proper 240 lugs.
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Bruce S. near D.C.

"...but you can not use the lug nuts from the 740."

You must not use them. Don't let your tire changer use them either. The problem is, one can use them, especially with the aid of an impact driver, and the result is the 1/2-20 studs are ruined and you'll possibly need to get 20 of them replaced on your hubs.
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Art Benstein near Baltimore

A man is flying in a hot air balloon and realizes he is lost. He reduces height and spots a man down below. He lowers the balloon further and shouts: "Excuse me, can you help me? I promised my friend I would meet him half an hour ago, but I don't know where I am."

The man below says: "Yes. You are in a hot air balloon, hovering approximately 30 feet above this field."

"You must be an engineer," says the balloonist.

"I am," replies the man. "How did you know?"

"Well," says the balloonist, "everything you have told me is technically correct, but I have no idea what to make of your information.

"The man below says, "You must be a planner."

"I am," replies the balloonist, "but how did you know?"

"Well," says the man, "you don't know where you are, or where you are going, and you have made a promise which you have no idea how to keep. The fact is you are in the exact same position you were in before we met, but now it is somehow my fault."

Yes. It'll be a direct swap with no issues. - Dave