My husband and I are planning a 10 day vacation in the beginning of June. We are debating going to either Seattle/Olympic NP/San Juan or Yellowstone/Grand Tetons/Jackson. I've heard both are wonderful. We do not have any children and enjoy hiking and rafting/kayaking. Last year we went to Yosemite and Big Sur and loved it. Please give me your input on which spot to choose. I would also welcome advice on iteneraries and items not to miss.
Thank you for your help!

With your itinerary of hiking, rafting and kayaking, I'd definitely go with the Yellowstone/Teton/Jackson combo.

Karen - It depends on where you live. If you are landlocked I'd say Olympic, otherwise you might prefer Yellowstone.
You can't go wrong with either one!
Not knowing where you live I would go with Olympic. Hurricane Ridge is spectacular! Take the ferry over to Victoria and the San Juans - great kayaking around the islands.
We were driving around Friday Harbor and watched a pod of Orcas casually go by. We spent about an hour in awe, heard the come by almost daily.

Karen,
Lived in Wash for 15 years and love, love, loved it. But have been to Yellowstone and Jackson twice and what a great place to visit. Paint pots, geysers, pools, hot springs, and then on to Jackson for a white water rafting trip. What fun .

Don't forget that June is the heavy month for tourists in the national parks. Yellowstone will be crawling with people of all size and shapes and age. Unless you get away from the normal tourist venue you're going to face a lot of people and automobile traffic. The Olympics, on the other hand, is big enough and remote enough to give you lots of space and privacy. You can hike the rain forest and you can also hike the Pacific coast section of the park. When you OD yourself on nature, you can flee to Seattle for seafood and java. I'm not from either Wyoming or Washington so I'm offering an unbiased opinion....

Yellowstone's thermal activity and the number of animals in the park make it incomparable with any other park, the beauty of any of the places you mentioned is a given; I would choose Yellowstone & Grand Teton in a flash. The landlocked comment by an earlier poster, however, is valid, so give that some consideration.

The hiking in Yellowstone is great - not enough people take advantage of the opportunities to get away from the roads (the usual National Park situation). I can't speak for the rafting/kayaking, as we're not into that. I would imagine you could go kayaking at Yellowstone Lake and some of the lakes in Grand Teton; June might be early in the season for rafting.

I disagree with the comment about the number of visitors to the parks. We visited Yellowstone and Grand Teton two years ago in mid-June, and were pleasantly surprised at the lack (comparatively speaking) of crowds. We stayed in W. Yellowstone, and the only time there was a traffic problem going in or out of the park, or elsewhere, was when a herd of bison wouldn't leave the road. The weather was cool, still, so if you go then, bring warm clothes.