Hi all,
Do I have to have Expansion pass if I want to buy and play Hearts of Stones? I cannot buy it. I don't know if it is bug or it is true. If so then Hearts of Stone doesn't cost 10Euro but 36Euro :(

Hearts of Stone is available separately. You can get it here.

Thanks for your answer.
I thought it too, but when I add this to the basket and click "Checkout now", the button "Pay for your order now" is grayed. And there is a clause "Please note that you are required to own Witcher 3: Wild Hunt, The - Expansion Pass on GOG.com to be able to purchase and play Witcher 3: Wild Hunt, The - Hearts of Stone" in the left side.

I tried putting it in the cart now (just to test if I would get the same message), and yeah, it does say the same thing for me.
I'm very very sure, however, that this is not meant to be this way (should probably state that you need to own the base game in order to play HoS). I guess you'll have to contact support so they can fix it?

OK. I will try support. I want to be sure I don't need the Expansion pass.