Flightboard app for iphone, ipad and Android is good for determining who flies where from your nearest airport.

Thinking they're neither so close nor so convenient to both visit in such a short time. Both are larger cities than Oslo.

I do not think that two days is enough to see both cities, at least not if you intend to visit the major museums in either city.

http://www.flickr.com/photos/mksfca/sets/72157623071349528/show/

http://www.flickr.com/photos/mksfca/sets/72157623070435704/show/

But it might be best to browse through guidebooks to see what each city has to offer.

I think two days is a bit short for both cities.
Both cities are definitly worth to see!
Copenhagen and Stockholm are the most beautiful cities in Scandinavia (Oslo and Helsinki is nothing special).

I highly recommend flying SAS from Dulles to either Copenhagen or Stockholm. IF you decide to do both, you can take a train or fly, but with limited time - I would fly between the cities.

We were in Copenhagen last April for 4 days and Stockholm for 5. We liked both cities a lot, but I would pick Copenhagen as the one if I was only going to do one city.

flysas.com they have a summer sale going on right now. We flew them and really like the experience.

we have been to both cities in the past 9 months both are beautiful. Be aware that both are very expensive! we were in stockholm in august and it was very warm but comfortable. the hop on bus is a good way to get to know the city. as long as you get on the top we have found the best way is to do the complete tour and when you start the second circuit get of at your first choice. if there are no upper deck do not bother with the lower just wait for the next bus.

we travelled to copenhagen in february and it was very cold -18. Having said that, my daughter was there in august and it was lovely weather.

in my opinion i would choose copenhagen for a short stay as it is very compact and everything is walkable. There is a danish design museum just past the royal palace which is really good .

IMO it would be preferable to choose one city and spend two days there instead of one day in each. Both cities are really great with so many things to see.

I would be hard pressed to choose one over the other. Late July/early August should give you some nice weather.

In Stockholm, you can buy a transit pass for all buses and ferries which makes it very easy to get around. We preferred Stockholm to Copenhagen, but both are beautiful waterfront cities so yo can't go wrong.